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"KRS/GT" Technical Q&A K1200RS/GT Technical Questions/Answers

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  #1  
Old 02-21-2011, 08:37 PM
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Transmission Final Drive Oil

I know this should be a simple question, but here goes. I just purchased a 2004 K1200RS with 8,500 miles. Just to be safe, I thought I would change the fluids, so I bought one of this website sponsor's recommended 75/90 synthetic gear lube. In reading the repair CD, however, I noticed the final drive called for straight 90 hypoid lube. As that is difficult to find except at the local marine store, I bought a quart of Belray straight 90 hypoid for the final drive from an on-line retailer.

Now, in looking at my owner's manual for another item, I came across the specs for the transmission, which, as I have now discovered, also calls for the straight 90 hypoid oil. So, should I not use the 75/90 synthetic GL 5 gear lube in either the transmission or final drive, or has the industry moved on the synthetics since my owner's manual was published?

I want to do it correctly, plus my drive train is as noisy as all get out. In other words, I am not worried about wasting the money on the 1.5 L of gear lube if the thing really needs the 90 hypoid.

Thanks!

Bradster
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  #2  
Old 02-21-2011, 08:54 PM
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Re: Transmission Final Drive Oil

Quote:
Originally Posted by Bradster
I know this should be a simple question, but here goes. I just purchased a 2004 K1200RS with 8,500 miles. Just to be safe, I thought I would change the fluids, so I bought one of this website sponsor's recommended 75/90 synthetic gear lube. In reading the repair CD, however, I noticed the final drive called for straight 90 hypoid lube.

I used 80W90 GL5 in the final drive for close to 90,000 miles in mine and my wife's 03 K1200RS without problems. I changed it every rear tire change.
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  #3  
Old 02-21-2011, 09:23 PM
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Re: Transmission Final Drive Oil

Lee,

How about in the transmission?

Bradster
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  #4  
Old 02-21-2011, 09:59 PM
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Re: Transmission Final Drive Oil

I have used 75/140 Syn and 75/90 syn. in tranny and rear drive. I did not feel any differance.

I change about every 6,000 with the engine oil, most times.

I like the 75/140 Syn
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  #5  
Old 02-21-2011, 10:40 PM
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Re: Transmission Final Drive Oil

I too used 75/140 synthetic, bought from the dealer in a BMW bottle (probably made by Spectro) no issues with the tranny or rear end to date.
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  #6  
Old 02-23-2011, 09:17 PM
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Re: Transmission Final Drive Oil

75/90 BMW and no problems
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  #7  
Old 02-24-2011, 06:52 AM
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Re: Transmission Final Drive Oil

Thanks guys. After reading an article from the transmission manufacturer, I am going with the straight 90 hypoid.

Bradster
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  #8  
Old 02-25-2011, 04:57 AM
voxmagna voxmagna is offline
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Re: Transmission Final Drive Oil

I think the problems posted here about rear drive failures have more to do with design than the actual oil used. I don't think any of the different oil specs mentioned will guarantee no future failure.

However, whatever oil is used, I've always thought it beneficial to change it regularly with engine oil changes. That way you remove any metal filings from the relatively small volume of oil in the drive and you get to inspect what comes out for any early warning signs of impending bearing doom.

The rear drive oil does actually get quite hot, but I'm not clever enough on oils to say in this application whether a wider band viscosity oil is much better than a fixed 90 grade. The only problem I saw once with a 'no-brand' cheap diff. oil was its tendency to foam due I suspect to detergent additives and that's the last thing you want to happen in a small gear enclosure. If you aren't sure, test an oil sample in a home liquidiser and see what happens.
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  #9  
Old 02-25-2011, 06:17 AM
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Re: Transmission Final Drive Oil

Quote:
Originally Posted by voxmagna
.... The rear drive oil does actually get quite hot....
I never thought about this but our 2002 K1200RS rear disc would get very hot. Someone on the site had a rear brake drag / fire problem due to improper pedal adjustment and since our RS was new I was making sure ours was OK. I checked it on our very first trip (wet finger smack test) and my fingers just bounced off due to the instant spit to steam. I thought it was going to need to go back to the dealer. Since the dealer was 150 miles away and BRPR was 50 miles away we went on to the i-bmw event.

Once there I walked around for three days checking rear disc when people would come in and park. The results were not as expected. Roughly 50% of the disc were cool, and the other 50% hot hot hot. There seemed no reason for this as the rear brake pedal adjustment felt fine on all of them.

In hindsight, of the rear drives that have failed I'd bet they are the "hot" ones. (Then again, we traded our RS at 67,000 miles and never had any problems.)
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Last edited by cabnfvr : 02-25-2011 at 12:56 PM.
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  #10  
Old 02-25-2011, 09:21 AM
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Re: Transmission Final Drive Oil

Quote:
Originally Posted by cabnfvr
In hindsight, of the rear drives that have failed I'd bet they are the "hot" ones. (Then again, our RS went 67,000 miles with no problems.)
Both of our bikes had the hot brake. The brake drag felt normal and we could go 30,000 miles on the rear pads. I never figured it out.
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  #11  
Old 02-27-2011, 12:01 PM
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Re: Transmission Final Drive Oil

I think the hot rear brake disc is a symptom of linked brakes or a heavy foot. What usually follows is your softer Kevlar pads are letting you know with the dust they kick up, or the HH pads are staying quiet until you need a new rotor!

Theoretically, the contribution of the rear brake to total braking effort is quite small, only around 15%. Many riders don't realise this and use more and more foot pedal which makes them feel comfortable, but there's no more stopping friction - just heating up and pads glazing over to reduce efficiency even more.

If your rear pads are knocked out at 4-6K then you probably are getting comfort from using the rear brake hard, with not much gain in stopping distance. My pads used to be shot at 6K when I first got the bike, now I use the rear brake less, mostly for the last hundred yards of slowing and at stops. Rear pads are now doing around 10K whilst fronts with engine braking are staying good for longer too.
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  #12  
Old 02-27-2011, 01:03 PM
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Re: Transmission Final Drive Oil

Like Shakespeare said... much ado about nothing!

The "recommended" oil is that which BMW themselves recommend. That is, plain ordinary 80W90 GL5 oil. It works perfectly fine. My old K100RS that (now sold to a friend's son) has had nothing but ordinary 80W90 GL5 in its transmission since day one. And "day one" was 22 years and 210,000 km ago. The tranny STILL shifts like the day it was bought.
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  #13  
Old 02-27-2011, 01:13 PM
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Re: Transmission Final Drive Oil

Quote:
Originally Posted by voxmagna
I think the hot rear brake disc is a symptom of linked brakes or a heavy foot.
Rear pads are now doing around 10K whilst fronts with engine braking are staying good for longer too.

I rarely used the rear brake lever. Mostly for parking lot turns and the last few feet when coming to a stop. If you're doing the same, I'm surprised you're only getting 10,000 Kilometers out of your back brake. If you meant 10,000 miles, even that seems low.
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  #14  
Old 02-27-2011, 03:25 PM
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Re: Transmission Final Drive Oil

Quote:
Originally Posted by voxmagna
I think the hot rear brake disc is a symptom of linked brakes or a heavy foot. ....
Nope. Too many checks at the end of long rides squash that theory. Some just drag more than others.
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Old 02-27-2011, 05:09 PM
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Re: Transmission Final Drive Oil

If they drag, the rotors are warped through excessive heat, or the pistons are sticking through heat, hardening of the piston seals or corrosion setting in.

When the calipers release there should be no significant drag, may be a 'scrape'. In UK bikes fail the annual DOT test if there is excessive drag which they measure on a brake test meter. If you put the bike on the center stand and can't run the rear wheel around in neutral with your toe, or it isn't rotating slowly due to drag in the drive line, then something is up.

Because there is only one rotor on the rear with a 4 pot caliper, unintentional heavy use and heating will harden up the pads and piston seals, as a lot of heat gets reflected back to the calipers. This process worsens the problem - drag increases, rotor and caliper gets hotter, caliper components get hotter, sticking pistons become seized pistons and won't retract off the rotor.

This happens less on cars because a) The rotors are in 2 sections with the center ventilated, and b) Their rotors normally have a thin sheet steel heat shield sitting between it and the caliper.

When you are riding you are not aware of any of this, but take off the caliper, hook it up to an air line and you may see some pistons moving at anything between 0.5 - 10 psi or higher, when they should all move at the lowest pressure. If only one piston is seized you will never know. The friction on the pads becomes uneven and because you apply brake pressure according to the slowing effect you expect, more heat can get generated in the working pad surfaces, causing more progressive piston sticking and seizures. These figures came from my own bike and after replacing piston seal rubbers, the pressures were all at the low end.

Instead of fitting brake pad indicators on later bikes that some have found troublesome and don't always work, BMW could have done something useful and provided feedback of the rotor temperatures. Something a regular mountain rider might appreciate.
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  #16  
Old 02-27-2011, 07:00 PM
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Re: Transmission Final Drive Oil

Quote:
Originally Posted by voxmagna
If they drag, the rotors are warped through excessive heat....
I seriously doubt that my checking of most of the roughly 105 K1200RS bikes at BRPR in 2002 constitutes a scientific test or meets the criteria of statistical analysis, but I'd sure bet my that there was nothing wrong with any of those bikes. Some just heat up more than others.

My sample lot.


BTW, that was one heck of an i-bmw event in those days.
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Old 02-27-2011, 07:01 PM
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Re: Transmission Final Drive Oil

Quote:
Originally Posted by voxmagna
If they drag, the rotors are warped through excessive heat, or the pistons are sticking through heat, hardening of the piston seals or corrosion setting in.

When the calipers release there should be no significant drag, may be a 'scrape'. In UK bikes fail the annual DOT test if there is excessive drag which they measure on a brake test meter. If you put the bike on the center stand and can't run the rear wheel around in neutral with your toe, or it isn't rotating slowly due to drag in the drive line, then something is up.


I stopped worrying about it when I saw we could both get 30,000 miles out of our rear pads. This was similar to the mileage we got on our K75S rear brakes.
The rear wheel would turn freely on both of our RSs.
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Old 03-05-2011, 01:23 PM
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Re: Transmission Final Drive Oil

Quote:
Originally Posted by cabnfvr
I seriously doubt that my checking of most of the roughly 105 K1200RS bikes at BRPR in 2002 constitutes a scientific test or meets the criteria of statistical analysis, but I'd sure bet my that there was nothing wrong with any of those bikes. Some just heat up more than others.
Some had linked brakes and some didn't? If so, I'm guessing the ones that were hot were either linked bikes or rider overusing the pedal. Judging from the rear pad wear on the linked bikes, I think the F-R proportioning is a little too biased rearward, at least for the normal lever pressures applied on the street.
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Old 03-05-2011, 02:06 PM
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Re: Transmission Final Drive Oil

Quote:
Originally Posted by cabnfvr
I seriously doubt that my checking of most of the roughly 105 K1200RS bikes at BRPR in 2002 constitutes a scientific test or meets the criteria of statistical analysis, but I'd sure bet my that there was nothing wrong with any of those bikes. Some just heat up more than others.

My sample lot.


BTW, that was one heck of an i-bmw event in those days.

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