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  #1  
Old 09-05-2008, 10:45 PM
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Next Gen. GT Final Drive Failure

At exactly 36,251 miles, after 1 year, 1 month, 1 week & 3 days of ownership, in Sturgis, South Dakota at approximately 9:30 pm on Thursday, September 4th, 2008 my final drive failed leaving my wife and I stranded!

We ended up taking a taxi to the Rapid City, SD airport and renting a one way car to Denver. We abandoned the motorcycle at Sturgis Yamaha, BMW, Suzuki awaiting warranty/repair info.

This is our first and last BMW motorcycle! The last 13 months have been a lesson in frustration.

No disrespect to the current owners of these machines, you are all among the finest motorcycling has to offer in riders!!! BMWs are amazing, less their problems. I wish you all well.

This site has been an enourmous help to my wife and I as we have trained for our 2009 Iron Butt Rally debut, but the bike is not upto the challenge. We will return to the much inferior Japanese motorcycles from which we came.

So long BMW!
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  #2  
Old 09-06-2008, 05:03 AM
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Re: Next Gen. GT Final Drive Failure

Sorry to hear it. Being left stranded by any vehicle sucks - I know, my first KS left me stranded in Florence, Italy ten days after I bought it (faulty clutch). Although I must admit that given the choice between being dumped in Florence or Sturgis - well, you got the real short end of the stick.

I'm just wondering, did you have lots of other problems with the bike or is this the only one? If so, what were they?

Good luck with whatever your next ride ends up being.
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  #3  
Old 09-06-2008, 08:43 AM
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Re: Next Gen. GT Final Drive Failure

was there any warning or symptoms prior to the final drive failure????? i'm displeased with my 2006 KS and would dump it for another bike if i could afford to. unfortunately i'm still a bit upside down on my loan and i'd take to big a financial hit if i opted out of the bike now, plus i doubt any dealer would give me a fair trade in based on all the bad press the new K bikes are getting.

there are a lot of things i really like about the BMW but the quality you expect from what is supposed to be a premium brand just isn't there.
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  #4  
Old 09-06-2008, 09:20 PM
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Re: Next Gen. GT Final Drive Failure

There were some indications....

1. With the bike on the center stand (right side case removed) with my hands at 3 & 9 O'clock or (6 & 12), the wheel wobbled slightly. Less than 1 mm of play 4500 miles before the failure.

2. for the last 3600 miles, I thought that I either had a defective front tire, or a front suspension problem as it seemed that I was constantly riding on a road with concrete expansion joints. The front tire seemed to 'slap' the road.

3. 20 miles before the failure, at slow speed coming to a stop, the rear of the bike shifted to the right. I thought to myself, "what the hell was that".

4. Grinding noise from the rear end.


Take note:

If your rear wheel has ANY play while rocking it side to side.....your final drive is failing. Get to a dealer and push them to replace it!
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  #5  
Old 09-06-2008, 09:53 PM
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Re: Next Gen. GT Final Drive Failure

Quote:
Originally Posted by helodoc
There were some indications....

1. With the bike on the center stand (right side case removed) with my hands at 3 & 9 O'clock or (6 & 12), the wheel wobbled slightly. Less than 1 mm of play 4500 miles before the failure.

2. for the last 3600 miles, I thought that I either had a defective front tire, or a front suspension problem as it seemed that I was constantly riding on a road with concrete expansion joints. The front tire seemed to 'slap' the road.


With all due respect...why did you not heed the warnings and have the bike fixed/looked at before heading out on a long 2 up journey.

Regardless of your response, I feel for your pain.
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  #6  
Old 09-06-2008, 10:01 PM
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Re: Next Gen. GT Final Drive Failure

Quote:
Originally Posted by helodoc
Take note:

If your rear wheel has ANY play while rocking it side to side.....your final drive is failing. Get to a dealer and push them to replace it!
That is not correct.

It is indeed correct for previous BMW rear drives (the ones without that big hole through the "axle"), but NOT for the latest generation rear drives.

The bearings in the previous generation rear drives were installed under preload, and as you stated, absolutely no play is permitted.

Latest generation rear drives have no bearing preload, and as a result can naturally have a slight amount of play.
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  #7  
Old 09-06-2008, 11:49 PM
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Re: Next Gen. GT Final Drive Failure

Quote:
Originally Posted by Flyboy
With all due respect...why did you not heed the warnings and have the bike fixed/looked at before heading out on a long 2 up journey.

Regardless of your response, I feel for your pain.

With all due respect....

The bike spent 2 weeks in the shop after our last 9,000 mile journey/just before this trip, where it had all 3 brake rotors replaced due to warpage, and all brake pads replaced. It also had a full service, and the final drive was addressed and determined, by the shop, to be in a serviceable condition!
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  #8  
Old 09-06-2008, 11:50 PM
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Re: Next Gen. GT Final Drive Failure

Quote:
Originally Posted by RFW
That is not correct.

It is indeed correct for previous BMW rear drives (the ones without that big hole through the "axle"), but NOT for the latest generation rear drives.

The bearings in the previous generation rear drives were installed under preload, and as you stated, absolutely no play is permitted.

Latest generation rear drives have no bearing preload, and as a result can naturally have a slight amount of play.

BULLSHIT!
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  #9  
Old 09-07-2008, 12:08 AM
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Re: Next Gen. GT Final Drive Failure

Quote:
Originally Posted by helodoc
BULLSHIT!
So tell me EXACTLY how you can get zero play when the main, large, deep groove wheel bearing supports the axle at one end, and a needle roller bearing (NOT a tapered roller, but a straight needle roller with NO thrust capability) supports the shaft at the other. Preloading is impossible.

The previous generation rear drives used a small tapered roller bearing opposite the big ball bearing, to preload the big ball bearing in thrust. This eliminated all play.

But the new rear drives cannot possibly preload the ball bearing because, as anyone with any engineering knowledge knows, the needle roller bearing that supports the "outboard" end of the rear axle has no thrust capability. NO needle roller bearing has any thrust capability.

As a result, the rear axle can float left-to-right, as much as the play in the big ball bearing will allow.... and you can look up the ball bearing specs in a bearing catalogue, to prove the main ball bearing, like ANY deep groove ball bearing, in fact DOES have a small amount of axial play.

This is all pretty basic mechanical engineering.
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  #10  
Old 09-07-2008, 01:40 AM
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Re: Next Gen. GT Final Drive Failure

Sorry, but Bob's correct.

Quote:
Originally Posted by helodoc
BULLSHIT!
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  #11  
Old 09-07-2008, 02:10 AM
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Re: Next Gen. GT Final Drive Failure

Quote:
Originally Posted by George_in_KG
Sorry, but Bob's correct.
Thanks George.

It clearly states in the new "K4x" BMW Repair DVD (of which I have a copy).... this is the one that covers all new generation K-bikes (K1200S/R/GT).... that side to side play, as measured at the rim of the rear wheel, of up to 1mm is acceptable.

So much for the "Bullshit" comment. Apology accepted! .

If the OP's dealer claimed that there can be no play at all, it is clear that the dealer is ignorant on this issue. Given that full instructions and specs are right there in the DVD repair manual, it makes me wonder about this dealer's competence.
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  #12  
Old 09-07-2008, 06:44 AM
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Re: Next Gen. GT Final Drive Failure

So, can anyone shed some light on what or why the failures occur? Is it assembly, engineering/design, poor quality gears, bearings, other components, lack of lubrication etc. ? I am curious - -Herb
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  #13  
Old 09-07-2008, 09:52 AM
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Re: Next Gen. GT Final Drive Failure

Geez, the guy's $20K motorcycle just stranded him in SD. Cut him a break. Maybe his diagnosis is correct that noticeable play (maybe more than 1mm) was a BAD sign.

Sorry for the bad luck? hopefully you find what you want. I've got a Jap and a German bike in the garage and am very happy.
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  #14  
Old 09-07-2008, 11:43 AM
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Re: Next Gen. GT Final Drive Failure

My bike has 32k miles so far no prob.. but I'm glad I bought an extended warranty, paid $1200 for 3 more years unlimited miles protection after I pass 36000. Figure one little breakdown like this and its more than paid for itself.

Good luck to everybody with mechanical problems.. sounds very frustrating.

L8r.. Allen
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  #15  
Old 09-07-2008, 11:48 AM
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Re: Next Gen. GT Final Drive Failure

Quote:
Originally Posted by RFW
Thanks George.

It clearly states in the new "K4x" BMW Repair DVD (of which I have a copy).... this is the one that covers all new generation K-bikes (K1200S/R/GT).... that side to side play, as measured at the rim of the rear wheel, of up to 1mm is acceptable.

So much for the "Bullshit" comment. Apology accepted! .

If the OP's dealer claimed that there can be no play at all, it is clear that the dealer is ignorant on this issue. Given that full instructions and specs are right there in the DVD repair manual, it makes me wonder about this dealer's competence.

I didn't apologize!

If can rock the wheel side to side, your final drive is failing!

RFW, you must be a koolaide drinking fool or a BMW dealer.
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  #16  
Old 09-07-2008, 12:37 PM
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Re: Next Gen. GT Final Drive Failure

Quote:
Originally Posted by helodoc
If can rock the wheel side to side, your final drive is failing!

RFW, you must be a koolaide drinking fool or a BMW dealer.
Neither of the above. I can simply read.

If you had bought the bike's service manual DVD, you would also be able to read the step by step instructions on how to check the rear end bearings too. The instructions right from BMW clearly state that a clearance of up to 1mm is normal.

Apparently, you are claiming that you know more about the rear drive than the people who designed it and who created the bike's service manual. If you actually understood something about the basic engineering principles of the new rear drives, you would realize how impossible your statement is. Unlike all previous rear drives made by BMW, the new generation rear drives does NOT preload the rear bearings (read the bloody service manual... it is all in there!). Without a preload, the deep groove main wheel bearing MUST have some axial clearance. It is impossible for any un-preloaded ball bearing to have zero axial clearance. Hence the 1mm clearance that BMW states is normal.

Obviously you have never read the repair manual, so maybe I should try to take a screen shot of the applicable section of the manual and post it. But you'd probably still claim you were right.
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  #17  
Old 09-07-2008, 01:02 PM
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Re: Next Gen. GT Final Drive Failure

Quote:
Originally Posted by Herb
So, can anyone shed some light on what or why the failures occur? Is it assembly, engineering/design, poor quality gears, bearings, other components, lack of lubrication etc. ? I am curious - -Herb
It is the bearings that go south... almost always the large deep groove "wheel bearing". Just before I sold it, I replaced it on my old K100RT (mind you it had nearly 200,000 km on it). There was an increasing amont of metal flakes being spalled off the bearing races and ending up on the drain magnet. This is a typical mode of non-catastrophic bearing failure as the bearing nears the end of its life.

On all BMW rear drives except the new generation ones, I believe it is incorrect factory bearing preload that causes the short life. This results in excessive bearing wear. Usually only the main ball bearing needs replacing, not the tapered roller that supports the other end of the axle, and supplies the preload.

Note also that with the preload shim measuring method that is stated in BMW's previous generation repair manuals, it is impossible to measure the preload accurately! The method requires using calipers to get two awkward reading, then subtract to two to get a shim thickness to an accuracy of better than 2 thousands of an inch! That means that EACH caliper reading MUST be accurate to much better than 1 thousandths of an inch! Calipers cannot resolve to this accuracy. Worse yet is that many dealers don't even measure and reshim the rear drive when the bearings are replaced. Rmeasuring accurately and reshimming is MANDITORY with new bearings because of normal bearing tolerances!! Small wonder that many rear drives that have been repaired by dealers, fail again!!!!

In some cases,the bearing retainer fails suddenly, allowing the balls to float willy-nilly all over the place. There has been a lot of evidence that the original 17-ball SKF bearings that BMW used were more robust because they had more room for a more robust ball retainer. At some point, BMW switched to Fischer (FAG) bearings that were dimensionally identical (both were #61917 with a "C3" axial clearance), but had 19 balls. Since most of the bearing retainer failures were with the FAG bearings, it has been thought that the closer ball spacing left less room for a robust retainer.

As for what causes the failure of new generation rear drives, there isn't enough statistical evidence yet, because there have been so few failures. One thing for sure... it is not caused by incorrect bearing preload, because in the new generation rear drives, there is no preload!
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  #18  
Old 09-07-2008, 02:01 PM
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Re: Next Gen. GT Final Drive Failure

Thanks for that info., Bob. At any rate, approx. 36000 miles (maybe 600 or 700 operating hrs. to failure) is unacceptable. I hope BMW will assist "helodoc" with repairs. Looks like he is out of warranty. Herb
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Old 09-07-2008, 05:38 PM
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Re: Next Gen. GT Final Drive Failure

Quote:
Originally Posted by Herb
Thanks for that info., Bob. At any rate, approx. 36000 miles (maybe 600 or 700 operating hrs. to failure) is unacceptable. I hope BMW will assist "helodoc" with repairs. Looks like he is out of warranty. Herb
It most certainly IS unacceptable. From his description is sounds like catastrophic failure of the large deep grove ball bearing's ball retainer. I have heard of this happening on previous generation rear drives, and it is puzzling. Has nothing to do with "wearing out".

Normally, when this bearing wears out on previous generation rear drives (especially when caused by excessive preload), it is a gradual process. In my case (on my old K100), over the space of several years and 40,000 km, I noticed an increasing amount of metal flakes stuck to the drain magnet. This is a typical bearing failure mode, where metal is spalled off the races. The rear drive never did fail, but I finally decided to replace the bearing and reshim and reassemble the rear drive.

I sold the bike a month ago. I live in Vancouver, and the bike was driven all the way across the continent takinwg numerous detours (over 6000 km) and is now in Nova Scotia.... and the new owner just loves it. So I must have done something right in the repair!
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Old 09-07-2008, 06:42 PM
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Re: Next Gen. GT Final Drive Failure

For those that are interested, attached is the "screen dump" of the applicable page of the BMW Repair Manual DVD for all the "K4x" series of bikes (K1200S/GT/R), showing the correct method of determining rear drive axial "play".

Notice that because the new generation rear drives are designed fundamentally differently than any rear drives in the past (i.e there is no bearing preload), BMW clearly states that up to 1mm of play as measured at the rear wheel rim is normal.

To view this jpeg without text fuzziness, you will probably need to maximize it to fill the screen.
Attached Images
File Type: jpg Rear Bearing Clearance.jpg (146.6 KB, 106 views)
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Old 09-07-2008, 09:45 PM
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Re: Next Gen. GT Final Drive Failure

You guys are getting mad at each other when you should be mad at BMW for selling such crap. As you said there may be a small amount failing but according to the polls on here and other sites, along with the other persistant issues, there is a QA issue that wouldn't be acceptable on any bike, much less a BMW.
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Old 09-07-2008, 11:46 PM
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Re: Next Gen. GT Final Drive Failure

Quote:
Originally Posted by bird
You guys are getting mad at each other when you should be mad at BMW for selling such crap. As you said there may be a small amount failing but according to the polls on here and other sites, along with the other persistant issues, there is a QA issue that wouldn't be acceptable on any bike, much less a BMW.
That statement is unfortunately too general. What is failing in any case is not the rear drive, but one of the bearings. The reason for the bearing failures is generally different in different bikes. Here is a summary as I know it....

Previous generation rear drives (without the big center hole through the axle):

- Incorrect bearing preload at the factory. This is emerging as a major problem.

- On repairs and later failures, Dealer Incompetence!!
*** Many dealers replace the main wheel bearing but leave the old shims in place. Idiots!! This is absolutely not premitted by BMW!! Each new bearing requires careful reshimming for correct preload. This is a very difficult task (I have done it myself, and it is more difficult than realigning a car's differential!).
*** Many (most??) mechanics lack the precise skill needed to accurately measure the dimensions needed to determine new shims, hence they return the bike to the customer with incorrect preload, resulting in early failure (again).

- Early catasrophic failure of the wheel bearing's ball retainer, especially on rear drives that have the 19-ball bearing made by FAG. The same bearing made by SKF has 17 balls and does not seem to have this problem.

Lastest generation rear drives:

- I'm guessing here, because there have been only a very few failures documented, but this is likely the same ball retainer failure as with the old drives.

But you are right... no matter what the "excuse" for failure, there is no excuse! Bevel gear drives and ball bearings, are not rocket science!
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- '08 K1200GT, metallic charcoal/silver
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  #23  
Old 09-08-2008, 01:15 AM
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Re: Next Gen. GT Final Drive Failure

Quote:
Originally Posted by bird
You guys are getting mad at each other when you should be mad at BMW for selling such crap. As you said there may be a small amount failing but according to the polls on here and other sites, along with the other persistant issues, there is a QA issue that wouldn't be acceptable on any bike, much less a BMW.

This is the correct answer. Thanks Bird.

But I did piss-off one of the die hard koolaid drinkers, that can regurgitate a service manual written by the same morons that designed this flawed shaft drive.

RFW besure to post up in 3 or 4 years when your bike actually reaches 36000 miles and the shaft fails, so I can laugh at you as well.
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  #24  
Old 09-08-2008, 01:45 AM
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Re: Next Gen. GT Final Drive Failure

Quote:
Originally Posted by helodoc
RFW besure to post up in 3 or 4 years when your bike actually reaches 36000 miles and the shaft fails, so I can laugh at you as well.
Well, since my last one got to 200,000 km, and still never failed, don't hold your breath!

BTW, in case you haven't figured it out, the failures have nothing to do with the "drive shaft". Also, it seems the text next to your avitar ("Lost in the dark") is rather fitting
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Old 09-08-2008, 02:03 PM
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Re: Next Gen. GT Final Drive Failure

Sorry to here about the bother with the final drive. My final drive failed at 9,000miles. As I understand the problem these final drives were supposed to be service free when they were first released ie - early models had no drain plug. 2008 models are now fitted with a drain plug. Basically the gears in the final drive during the running in period actually shave thereselves which means as they run in mesh small fragments of steel are shaved from the teeth until they bed thereselves in. Hence the final drives needed the oil changing at the first service, but earlier models didnt seem to get the service so the failures started to occur. These fragments of steel contaminate the bearings and cause them to fail. As you say the 1mm of play at the rear wheel rim is as the manual states is acceptable. Some people appear to think that the ball race is the issue but in my final drive it was the needle roller bearing that failed, causing excessive play. To my dismay the dealer repaired my final drive with the fitting of one needle bearing, my arguement being if one of the bearings was damage it would follow that the other three bearings in the final drive must have suffered the same. As you can imagine I was not happy! I am still trying to negotiate with BMW as this happened within warranty that if they think the repair is satisfactory and would be no further trouble they will have no quarms in extending the warranty of the final drive. As you mentioned the problem with your brake rotars, I too am on the second set plus originals. Apparently the latest rotors or manufactured in a different way as to aleviate the problem of distorting. You were quite lucky as they never replaced my pads until the brake pad indicator warning light wire became detatched and then they only replaced the one set ie - right hand side. I then had the privilage of paying £50 for the other side!!!! Suppose it could have been worse the side with the sensor are £65. I too will probably not be buying another BMW (Bite My Wallet) as we say! Oh forgot to mention the new air box, ews sensor ring and the shit seats! Thanks
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Old 09-08-2008, 05:45 PM
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Re: Next Gen. GT Final Drive Failure

Quote:
Originally Posted by pkrich
Basically the gears in the final drive during the running in period actually shave thereselves which means as they run in mesh small fragments of steel are shaved from the teeth until they bed thereselves in.
Sorry, that is NOT correct. The final drive gears already undergo a high precision gear shaving/polishing process in manufacturing. First the gears are hobbed on a standard gear hobbing machine, then they are put into a gear shaving machine for final finishing.

It is important to realize that the bevel gear teeth in the rear drive do NOT rub against each other. They are designed so their teeth ROLL against each other. Without any rubbing or sliding action (between mated teeth), how is it possible that they can "shave" off bits of metal?? Answer: they cannot!

Gears emphatically do NOT shave themselves in operation, and they do NOT "bed themselves in" either! This is an old wives tale that (as engineering students) we were told emphatically was BS. The reason for changing the oil after the first thousand km is mainly to flush out any possible machining residues.
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Old 09-08-2008, 06:02 PM
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Re: Next Gen. GT Final Drive Failure

Quote:
Originally Posted by RFW
Sorry, that is NOT correct. The final drive gears already undergo a high precision gear shaving/polishing process in manufacturing. First the gears are hobbed on a standard gear hobbing machine, then they are put into a gear shaving machine for final finishing.

It is important to realize that the bevel gear teeth in the rear drive do NOT rub against each other. They are designed so their teeth ROLL against each other. Without any rubbing or sliding action (between mated teeth), how is it possible that they can "shave" off bits of metal?? Answer: they cannot!

Gears emphatically do NOT shave themselves in operation, and they do NOT "bed themselves in" either! This is an old wives tale that (as engineering students) we were told emphatically was BS. The reason for changing the oil after the first thousand km is mainly to flush out any possible machining residues.

Gears do slide. They only roll at precisely the pitch diameter. They slide into mesh, (the arch of approach) and slide out (the arch of recession). They have been trying to invent gears that only roll for bout 100 years. Ain’t happened yet.
If the gearbox is designed properly and the gears are properly hardened there should be no metal “shaved”. However I have never seen a gearbox that does not have metal residue on the magnetic plug and it ain’t always residue from manufacture.
Gears do wear in particularly gears that are a little less than perfect.
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Old 09-08-2008, 10:58 PM
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Re: Next Gen. GT Final Drive Failure

Helodoc,

I think you are misinterpreting Bob's response. He is simply stating that BMW allows 1mm of axial play in the final drive. This is a factual statement based on the BMW service literature. Play in excess of 1mm in the axial direction OR play in other axes would very well indicate a possible upcoming failure of the final drive.

We are with you, brother. It would absolutely suck to be stranded by a new machine while far from home. Don't forget that this a mechanical system and unexpected failures can happen.


Quote:
Originally Posted by helodoc
I didn't apologize!

If can rock the wheel side to side, your final drive is failing!

RFW, you must be a koolaide drinking fool or a BMW dealer.
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Old 09-08-2008, 11:53 PM
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Re: Next Gen. GT Final Drive Failure

Quote:
Originally Posted by George_in_KG
I think you are misinterpreting Bob's response. He is simply stating that BMW allows 1mm of axial play in the final drive. This is a factual statement based on the BMW service literature.
That is partly what I was trying to communicate, George. Note that with previous generation rear drives, NO amount of axial play was acceptable!

The other point is that there MUST be some axial play in a new generation rear drive. It is impossible for there not to be. The large wheel bearing is a deep grove ball bearing. ALL bearings of this type have axial play by basic design. In previous generation rear drives, the bearing at the other end of the "axle" was a tapered roller, and it was used to provide end-thrust and preload, to eliminate the natural play in the ball bearing.

New generation rear drives do not have a tapered roller to supply thrust, hence preload is impossible. The bevel gears are designed to accept the limited amount of axial "float" that the ball bearing has.

Quote:
Play in excess of 1mm in the axial direction OR play in other axes would very well indicate a possible upcoming failure of the final drive.
Yes. Specifically, the impending failure of one of the bearings (usually the big deep groove ball bearing). The actual gears almost NEVER fail... only the bearing.
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Old 09-09-2008, 12:02 AM
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Re: Next Gen. GT Final Drive Failure

Quote:
Originally Posted by DEPARKER1817
Gears do slide. They only roll at precisely the pitch diameter.
I wondered if you would catch that! You are right, of course.... I was being intentionally a little simplistic. The actual amount of sliding motion (away from the pitch diameter) is still relatively minor. What I was trying to do is correct the notion that spur or bevel gear teeth undergo heavy sliding motion between their teeth.

Worm and hypoid gear sets are a different situation and they have such a high amount of sliding action between teeth, that without the use of Hypoid gear oil, these gear sets will have a very short life.
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Old 09-09-2008, 04:43 AM
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Re: Next Gen. GT Final Drive Failure

Quote:
Originally Posted by pkrich
Sorry to here about the bother with the final drive. My final drive failed at 9,000miles. As I understand the problem these final drives were supposed to be service free when they were first released ie - early models had no drain plug. 2008 models are now fitted with a drain plug. Basically the gears in the final drive during the running in period actually shave thereselves which means as they run in mesh small fragments of steel are shaved from the teeth until they bed thereselves in. Hence the final drives needed the oil changing at the first service, but earlier models didnt seem to get the service so the failures started to occur. These fragments of steel contaminate the bearings and cause them to fail. As you say the 1mm of play at the rear wheel rim is as the manual states is acceptable. Some people appear to think that the ball race is the issue but in my final drive it was the needle roller bearing that failed, causing excessive play. To my dismay the dealer repaired my final drive with the fitting of one needle bearing, my arguement being if one of the bearings was damage it would follow that the other three bearings in the final drive must have suffered the same. As you can imagine I was not happy! I am still trying to negotiate with BMW as this happened within warranty that if they think the repair is satisfactory and would be no further trouble they will have no quarms in extending the warranty of the final drive. As you mentioned the problem with your brake rotars, I too am on the second set plus originals. Apparently the latest rotors or manufactured in a different way as to aleviate the problem of distorting. You were quite lucky as they never replaced my pads until the brake pad indicator warning light wire became detatched and then they only replaced the one set ie - right hand side. I then had the privilage of paying £50 for the other side!!!! Suppose it could have been worse the side with the sensor are £65. I too will probably not be buying another BMW (Bite My Wallet) as we say! Oh forgot to mention the new air box, ews sensor ring and the shit seats! Thanks

The most important piece of information you contributed was that the needle roller bearing had failed.

I can admit to a similar failure caused by my own fault repairing an older KRS drive:

If you are referring to the pinion needle bearing, it is massive and I doubt very much that it could 'fail' with such low mileage.

However, If the pinion nut has worked loose (yes it can!) because it wasn't torqued down sufficiently to the enormous torque figure or the Loctite didn't hold (and this is one of those places where Loctite has to work) you have big problems.

The pinion to crown gear mesh will be horribly wrong, 'shaving' as you call it will occur and metal particles will appear in the oil.

I would definitely be asking the dealer whether the pinion nut was loose when the drive was first examined because that could cause a rear drive failure or seizure at high speed. I would have asked for a replacement drive, since these metal particles would have entered the remaining bearings and seals and the condition of the crown and pinion gears would be suspect. If they replaced any of the shims then you can be confident they went through the drive setup procedure but wonder if wear on the gears now required the change. If there are no shims charged on the parts invoice, you can guess what they did.
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Old 09-09-2008, 08:38 AM
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Re: Next Gen. GT Final Drive Failure

I understand what RFW is saying, I also understand the difference between the shaft & final drive.....

My point is that regardless of what the service manual says or RFW preaches, that anything near 1mm of play, your final drive is in the early stages of failure. I don't care what the manual says. I got the same story when my mechanic called the BMW tech rep.

Think about it. If you can rock that wheel fore & aft, then the wheel will have an eccentric rotation...eventually causing the bearing to fail.

When the next final drive develops play, I will be right back at BMW raising hell until they warranty another final drive regardless of the measured play, or the limit in the book.

I think some folks are in denial. Unwilling to accept the fact that they spent $20k + on a motorcycle that in all likelyhood will leave them stranded.

Besides, someone wants to make this a discussion of what's considered acceptable play, when the real issue is that BMW is selling a defective product, and has refused acknowledge their failings. It's certainly not MY fault that this piece of crap failed. This motorcycle was supposed to be the solution to several criteria we wanted in a new motorcycle. It is fast, comfortable, and loaded with options, but if you can't trust the engineering, and technology you are sitting upon, then $20,000 right in the toilet.
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Old 09-09-2008, 09:10 AM
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Re: Next Gen. GT Final Drive Failure

Quote:
Originally Posted by helodoc
I understand what RFW is saying, I also understand the difference between the shaft & final drive.....

My point is that regardless of what the service manual says or RFW preaches, that anything near 1mm of play, your final drive is in the early stages of failure. I don't care what the manual says. I got the same story when my mechanic called the BMW tech rep.

Think about it. If you can rock that wheel fore & aft, then the wheel will have an eccentric rotation...eventually causing the bearing to fail.

When the next final drive develops play, I will be right back at BMW raising hell until they warranty another final drive regardless of the measured play, or the limit in the book.

I think some folks are in denial. Unwilling to accept the fact that they spent $20k + on a motorcycle that in all likelyhood will leave them stranded.

Besides, someone wants to make this a discussion of what's considered acceptable play, when the real issue is that BMW is selling a defective product, and has refused acknowledge their failings. It's certainly not MY fault that this piece of crap failed. This motorcycle was supposed to be the solution to several criteria we wanted in a new motorcycle. It is fast, comfortable, and loaded with options, but if you can't trust the engineering, and technology you are sitting upon, then $20,000 right in the toilet.
I feel for you. Failure of the final drive is inexcusable even at 100K. Bob is right about the small amount of axial play a ball and needle combination will have. If it doesn’t have any play the bearing will be preloaded and you may be in trouble. However, it is important to distinguish between axial play along the wheel axis and radial play along the other axis. If you can grab the wheel at the 9 and 3 o’clock position (push with one hand and pull with the other) and rock it back and forth (wobble) it has radial play. Any radial play (that you can feel) is an indication that the bearings are failing, particularly if it gets progressively worse. From your description of your problem I think that this exactly what happened.
I have been a loyal BMW customer since 1985 and I pay a premium for the marquee. I service my bikes (1985 K and 2005K) regularly and I expect long life. If I get stranded in South Dakota or even East Dakota I will be one pissed off customer and would likely take my business else where.
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Old 09-09-2008, 09:10 AM
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Re: Next Gen. GT Final Drive Failure

"My point is that regardless of what the service manual says or RFW preaches, that anything near 1mm of play, your final drive is in the early stages of failure. I don't care what the manual says. I got the same story when my mechanic called the BMW tech rep."
Keep in mind that the given dimension is taken maybe 8" from the axis. It is therefore magnified and the actual clearance in the bearing is less. You have to have some point of reference to determine if the assembly is OK or not OK. If there is no clearance, excessive heat will be generated and will also contribute to failure. BMW will never release the results of a root cause analysis.

This discussion does not help your situation and it is a shame that such a basic Axel layout has failed. Herb
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Old 09-09-2008, 09:13 AM
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Re: Next Gen. GT Final Drive Failure

Thanks you for clarifying...I was refering to radial play. Thought I mentioned the 3&9 or 6&12 o'clock positions in my original post.

Appreciate it.
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Old 09-09-2008, 10:54 AM
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Re: Next Gen. GT Final Drive Failure

Found some pix of the newest FD being taken apart and put back together. Just so y'all can see what it looks like inside...
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Old 09-09-2008, 11:52 AM
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Re: Next Gen. GT Final Drive Failure

Thanks, excellent pictures. Herb
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Old 09-09-2008, 12:50 PM
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Re: Next Gen. GT Final Drive Failure

Quote:
Originally Posted by chuba
Found some pix of the newest FD being taken apart and put back together. Just so y'all can see what it looks like inside...
Excellent photos indeed! They clearly show the use of a straight roller bearing instead of a tapered roller like previous generation rear drives used, hence the absolute impossibility of applying a preload to the main (large) deep groove wheel bearing.

Because a preload in not possible, it is obvious that the system is intentionally designed to allow the small axial play that ANY deep groove ball bearing MUST have. This is the source of the maximum allowed 1 mm of play (measured at the rim) that BMW states.
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Old 09-09-2008, 01:18 PM
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Re: Next Gen. GT Final Drive Failure

Quote:
Originally Posted by Herb
Keep in mind that the given dimension is taken maybe 8" from the axis. It is therefore magnified and the actual clearance in the bearing is less. You have to have some point of reference to determine if the assembly is OK or not OK. If there is no clearance, excessive heat will be generated and will also contribute to failure. BMW will never release the results of a root cause analysis.
You have hit the nail on the head, Herb.

The 1mm allowable play is in fact the bearing play magnified about 15-20 times as a result of the ratio of the center-to-rim distance, as compared to the center-to-bearing-race distance.

A perfectly normal 1-2 thousandths of an inch bearing axial clearance (and if one consults the actual bearing specs,this is indeed normal.... ALL ball bearings MUST have some axial clearance!), will be easily magnified to up to a millimeter play, when it is measured at the rim.

Those that claim a 1mm axial play is unacceptable when measured at the rim, are really just complaining about 1-2 thousandths of an inch at the actual bearing, and if one look up the specs on the bearing, one will see this axial clearance is intentionally built into any ball bearing.

The important point to be taken from this is that it is utterly impossible for the new generation rear drive to have zero play! A small amount of axial play MUST occur, because there isn't a ball bearing made that has zero axial play!

More to the point, this new rear drive design ELIMINATES the basic problem the old drives had.... namely the need for a VERY difficult to achieve preload of 0.05 ~ 0.10mm (a mere 2 to 4 thousandths of an inch!). This tiny amount of preload was difficult to accurately achieve, both at the factory, and especially by ham-fisted bike mechanics (many of whom never even bothered, and just replaced the old shims!).The gearset is designed to accept this small amount of bearing end float. The fact that this is magnified by the time it is meaured at the rim, makes no difference.
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Old 09-09-2008, 01:32 PM
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Re: Next Gen. GT Final Drive Failure

Quote:
Originally Posted by helodoc
Think about it. If you can rock that wheel fore & aft, then the wheel will have an eccentric rotation...eventually causing the bearing to fail.
You fail to understand the basic engineering concept here. There MUST by definition be axial (and a smaller amount of radial) play in an un-preloarded system like this.

The ONLY thing that allows any play in the first place, is the bearing itself. The axle is supported at one end by a standard deep groove ball bearing, and at the other end by a straight (non-tapered) roller bearing. The only thing that limits how far the axle can move axially, is the normal play in the ball bearing. If a ball bearing has axial play (and they ALL do), then it will by definitition ALSO translate into a small amount of radial play (they all have some of that, as well). There is no way around this, except to preload the system, and the preload is what caused much of the reliability problems with old drives.

So what you are saying, is that the normal and unavoidable play that any ball bearing has, is proof that it will fail!

This makes no sense.
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Old 09-09-2008, 01:35 PM
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Re: Next Gen. GT Final Drive Failure

Let me make this simple for you wizard.....

The simple fact that it's attached to a BMW, means it will fail!
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Old 09-09-2008, 02:46 PM
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Re: Next Gen. GT Final Drive Failure

Quote:
Originally Posted by chuba
Found some pix of the newest FD being taken apart and put back together. Just so y'all can see what it looks like inside...

Hey Chuba
Great pictures.
What is the reason for taking the rear apart? The roller bearing has not yet failed from what I can tell from the pictures. However the discoloration of the shaft concerns me. The shaft is actually the inter race of the bearing. It appears that the color is almost a dark blue. This is a sign of excessive heat. I am wondering if the roller bearing is being adequately lubricated. Hard to tell just by looking at the pictures, but it looks suspect.
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Old 09-09-2008, 03:19 PM
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Re: Next Gen. GT Final Drive Failure

Quote:
Originally Posted by helodoc
Let me make this simple for you wizard.....

The simple fact that it's attached to a BMW, means it will fail!
From some of the other post I guess your rear drive didn't fail. Why did you call the taxi?
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Old 09-09-2008, 03:28 PM
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Re: Next Gen. GT Final Drive Failure

Quote:
Originally Posted by DEPARKER1817
However the discoloration of the shaft concerns me. The shaft is actually the inter race of the bearing. It appears that the color is almost a dark blue. This is a sign of excessive heat. I am wondering if the roller bearing is being adequately lubricated. Hard to tell just by looking at the pictures, but it looks suspect.
I wondered about that too, but in order for the shaft to turn blue, a LOT of heat would be needed (because of the large mass of the shaft). But since the heat would have to come from bearing friction, the much smaller bearing rollers would also have to have gotten even hotter! Yet there seems no real evidence of this. I have had similar failures of roller bearings (the big end of 2-stroke con rods), and overheating always was evidenced by the rollers themselves turning blue; the large crank pins never really got hot (because of their mass)

Also, there is relatively less load on the roller bearing. The big deep groove ball bearing is carrying most of the load from the gears (it is closer to the crown gear than the roller is). So that really makes the discoloration of the shaft a bit mysterious.
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Old 09-09-2008, 03:41 PM
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Re: Next Gen. GT Final Drive Failure

Quote:
Originally Posted by RFW
I wondered about that too, but in order for the shaft to turn blue, a LOT of heat would be needed (because of the large mass of the shaft). But since the heat would have to come from bearing friction, the much smaller bearing rollers would also have to have gotten even hotter! Yet there seems no real evidence of this.

Also, there is relatively less load on the roller bearing. The big deep groove ball bearing is carrying most of the load from the gears (it is closer to the crown gear than the roller is). So that really makes the discoloration of the shaft a bit mysterious.

It is not a load issue. If I had to guess, and that is what I am doing. If the level was a little low and you are just riding down the slab, you know not flicking it back and forth maybe it is running dry. The sump is very small, therefore if you are a couple oz. low it could make a difference in the level.
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Old 09-09-2008, 04:50 PM
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Re: Next Gen. GT Final Drive Failure

Quote:
Originally Posted by DEPARKER1817
It is not a load issue. If I had to guess, and that is what I am doing. If the level was a little low and you are just riding down the slab, you know not flicking it back and forth maybe it is running dry. The sump is very small, therefore if you are a couple oz. low it could make a difference in the level.
Actually, looking at the photo again, I am wondering if it is discoloration at all. It could just be the normal appearance of the shaft having been "rolled on", and accented by the camera. Note that the area in question is very precisely defined, which should not be the case if it was caused by heat.

Maybe the guy just wanted to replace that gibbled-looking oil seal!
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  #47  
Old 09-09-2008, 09:45 PM
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Re: Next Gen. GT Final Drive Failure

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  #48  
Old 09-09-2008, 10:33 PM
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Re: Next Gen. GT Final Drive Failure

Quote:
Originally Posted by RFW
I wondered about that too, but in order for the shaft to turn blue, a LOT of heat would be needed (because of the large mass of the shaft). But since the heat would have to come from bearing friction, the much smaller bearing rollers would also have to have gotten even hotter! Yet there seems no real evidence of this. I have had similar failures of roller bearings (the big end of 2-stroke con rods), and overheating always was evidenced by the rollers themselves turning blue; the large crank pins never really got hot (because of their mass)

Also, there is relatively less load on the roller bearing. The big deep groove ball bearing is carrying most of the load from the gears (it is closer to the crown gear than the roller is). So that really makes the discoloration of the shaft a bit mysterious.

Will somebody point out the Deep Groove ball bearing. All I see is a roller bearing on the crown wheel side and a much smaller needle on the opposite side. I realize the pinion gear has probably tapered roller bearings to take the thrust, but I don't see a ball bearing. Do any of you? What takes the side thrust of the pinion gear on the crown gear? I had a K100 that wasted the big ball bearing at about 60K miles and I replaced it and did a remeasure and found it was preloaded too much. RFK is right about that.

H
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  #49  
Old 09-09-2008, 10:49 PM
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Re: Next Gen. GT Final Drive Failure

Quote:
Originally Posted by DEPARKER1817
What is the reason for taking the rear apart?
Don't know - that's someone else's FD disassembly pix I stumbled across.

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  #50  
Old 09-10-2008, 12:05 AM
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Re: Next Gen. GT Final Drive Failure

Quote:
Originally Posted by hgp3
Will somebody point out the Deep Groove ball bearing.
You cannot see it. It is hidden between the back side of the crown gear, and the outer cover. He never took it apart far enough. To remove it, is a bit of a PITA.

Quote:
I realize the pinion gear has probably tapered roller bearings to take the thrust, but I don't see a ball bearing.
Actually, no. The pinion gear mounts in a special angular contact ball bearing set (2 angular contact ball bearings in one housing. Angular contact ball bearings have a very high thrust rating.

Quote:
What takes the side thrust of the pinion gear on the crown gear?
The side thrust of the crown gear is taken up by the large deep groove ball bearing. That is why they use a deep groove ball bearing, which is rated at higher thrust loads as compared with a normal ball bearing.

Quote:
I had a K100 that wasted the big ball bearing at about 60K miles and I replaced it and did a remeasure and found it was preloaded too much. RFW is right about that.
I just replaced the same bearing on my old K100RT 2 months ago before I sold it. It had 200,000 km on it, and was starting to go. It too seemed to have a little too much preload. And measuring the proload the way BMW says to do it (balancing a pair of calipers upright, and attempting to make 2 separate "end" measurements that have to be accurate to less than 1 thousandths of an inch) is virtually impossible. Small wonder so many rear drives that were repaired, fail again. It would be bad enough if the mechanics actually tried to measure the preload that way, but worse is that most of them dont even bother... they just reuse the old shims! Far too many mechanics simply do not understand engineering basic concepts and have a hard time reading and following instruction given by BMW, as well.
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  #51  
Old 09-10-2008, 04:58 PM
bridwell52 bridwell52 is offline
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Re: Next Gen. GT Final Drive Failure

My 07 GT has 26,000 trouble free miles except for the brake light thing. It was fixed by the dealer, both front pads. I keep reading about FD failures and air boxes, warp rotors and bad batteries. Its to the point I feel nervous on every trip.
If my bike gives me problems it is gone, plain and simple. If it doesnt then I will continue to enjoy it.
A FD failure would be the kiss of death.
David
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  #52  
Old 09-10-2008, 08:40 PM
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Re: Next Gen. GT Final Drive Failure

Quote:
Originally Posted by bridwell52
A FD failure would be the kiss of death.
It is "just" a bearing replacement. Having just done this myself on my old '86 K100 (at 200,000km), and also having fully reviewed the step-by-step process on the BMW Service DVD for my new GT (out of interest only), it is clear that bearing replacement for the new generation rear drives is a lot less difficult for the new rear drives.

It might be an annoying inconvenience, but a do-it-yourself rear drive bearing replacement is nowhere close to the "kiss of death". With no need for the extreme accuracy needed to (awkwardly) measure bearing preload that the old rear drives needed, the wheel bearing replacement on the new rear drives is almost straightforward.

All that said, I believe the new rear drives will generally be shown to be far more reliable than the old ones. The elimination of the troublesome bearing preload (that requires a LOT of skill to measure) eliminates the cause (in my view) of most of the bearing failures that so many old rear drives had.
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  #53  
Old 09-10-2008, 11:00 PM
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Re: Next Gen. GT Final Drive Failure

[quote=RFW]That is not correct.

It is indeed correct for previous BMW rear drives (the ones without that big hole through the "axle"), but NOT for the latest generation rear drives.

The bearings in the previous generation rear drives were installed under preload, and as you stated, absolutely no play is permitted. I just looked and your right. From what I see it relies on shimming for the bevel gears. Which have a low tolerance for slop. One ball bearing and a small needle bearing. Good news is it looks fairly simple to re shim as the miles go on.
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  #54  
Old 09-10-2008, 11:29 PM
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Re: Next Gen. GT Final Drive Failure

Quote:
Originally Posted by biff
The bearings in the previous generation rear drives were installed under preload, and as you stated, absolutely no play is permitted. Any tappered roller bearing requires a preload. Your telling us that there are none in the new k final drive?
Yes. The previous generation rear drives needed to have no axial play in the main "axle" that the wheel was bolted to. To achieve zero play, preloading was necessary. This was mainly needed, not because of the bearings, but to keep the exact clearances between the bevel gear teeth unchanged under all load conditions. This was achieved by having a tapered roller pressing against the "axle" and holding the large ball bearing at the opposite end, under compression (the preload).

New generation rear drives do things differently. There is still the big deep-groove ball bearing (that some have called the "wheel bearing"). But at the opposite end of the "axle", the tapered roller has been replaced by a standard roller bearing. Because the roller bearing is incapable of applying axial force (preload) on the "axle", the big ball bearing has no preload. It is free to move very slightly (1-2 thousandths of an inch only) in an axial direction as a result of its own small amount of clearance between balls and races. No ball bearing has zero axial play; all have a small amount of play by design.

The bevel gearset is designed to accept this small amount of axial play without any additional wear.

This design totally eliminates the serious problem of getting the amount of preload within the very narrow limits (between a mere 2 and 4 thousandths of an inch) that the previous rear drives needed.
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  #55  
Old 09-12-2008, 04:13 PM
pkrich pkrich is offline
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Re: Next Gen. GT Final Drive Failure

Can I just ask, I am not the only one dissatisfied with BMW quality, has anybody approached BMW with their individual complaints? We have the BMW customer services and we are getting nowhere fast. If everybody approached BMW with these issues we all might get somewhere? They are doing a very good job of avoiding admitting or answering any questions.
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  #56  
Old 09-13-2008, 11:26 AM
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Re: Next Gen. GT Final Drive Failure

I had a Honda VFR that had its wiring harness take a crap on a trip, the dealer had it for over 2 weeks when I sent a letter to ma Honda stating my disapointment and enclosed a CD with pages of complaints from VFR forums about the VFRs electrical problems. My bike was fixed after 1 month at the dealer, I traded it for my KGT 2 days later. I recieved a recall notice from Honda a few weeks later for the same wiring harness replacement that my bike needed when it went to the shop. I dont know if my letter did anything to cause the recall but it made me feel better.

I also had a KTM dirt bike bought back from KTM after sending just such a letter! It had a needle bearing floating around in the engine that ended up stuck to the magnetic drain plug!

Complain by snail mail it carries more weight
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  #57  
Old 09-15-2008, 10:21 AM
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Re: Next Gen. GT Final Drive Failure

YES, The BMW final drive is a piece of junk. If it was left on a 75HP bike it is fine but not on anything with some HP. If it was as simple as a better bearing or preload or washing out the grit from manufacturing they would have done it. Fact is it is to small of a part for what it is asked to be doing. Why cant they just use a twin sided swing arm with something other than a chain on it. On my 03 GT there is over 34K with no problems. On my 08 so far so good. Change the drive oil at 100 , 600 , 2500 than every oil change. If it comes out dirty than change more often.
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  #58  
Old 09-15-2008, 12:14 PM
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Re: Next Gen. GT Final Drive Failure

KKM,

RFW should be along shortly to inform you that you are 'incorrect', then site pages of useless babble from a dvd service manual about why you're incorrect, then defend BMW's high quality engineering to a fault.

In the end, wishing you 'good luck' with your '08 final drive is just as useful.

Good luck....may the final drive be with you!
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  #59  
Old 09-16-2008, 04:35 AM
billbeemer billbeemer is offline
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Re: Next Gen. GT Final Drive Failure

bmw is living in the past with drive shafts and needs to get with the improved technology of a rear belt. oh, i know, this is where u guys are going to say a belt wont take all that horsepower. the company has lost a big chunk of their quality reputation by leaving riders on the side of the road with faulty fd's. exhibit #1, the new buell, with the rotax engine. 150hp with a rear belt. dependable, simple, and hundreds of dollars less to build. will the germans change, or end up like the limeys. remember triumph, bsa, norton and enfield? their mantra was "who needs electric start"? get it, berlin?
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  #60  
Old 09-16-2008, 09:34 AM
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Re: Next Gen. GT Final Drive Failure

Quote:
Originally Posted by billbeemer
bmw is living in the past with drive shafts and needs to get with the improved technology of a rear belt. oh, i know, this is where u guys are going to say a belt wont take all that horsepower. the company has lost a big chunk of their quality reputation by leaving riders on the side of the road with faulty fd's. exhibit #1, the new buell, with the rotax engine. 150hp with a rear belt. dependable, simple, and hundreds of dollars less to build. will the germans change, or end up like the limeys. remember triumph, bsa, norton and enfield? their mantra was "who needs electric start"? get it, berlin?

The Buell on display at Indy, the version that they race has a chain. I guess Buell Racing is not privey to the new belt technology.
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