Rear Drive III

[mogu83]

Has anyone noticed that the newer Rs and RTs have a breather (vent) in the rear drive. Do you think they (we) might have had a pressure building up problem in the old drive.




Part #8 Interesting

[hjsbmw]

Has anyone noticed that the newer Rs and RTs have a breather (vent) in the rear drive. Do you think they (we) might have had a pressure building up problem in the old drive.

Hadn't noticed that. Over pressure could certainly accelerate seals starting to leak, and it would also raise the temperature, which can cause other problems, I guess. I'll refrain from wild speculations. I would think that BMW putting a pc valve there, effectively increasing the manufacturing cost, has a reason.

[omg1010]

All the newer 1200 models have the modified final drive. Originally the final drive just had a life-long oil filling of 220 mL. The "old" final drive also had one screw for eventually draining the oil on the rear end and not on the bottom end. Then BMW discovered problems and released an advise to change the oil every 20 000 kms. And the quantity was reduced to 180 mL. The reason was that foam built up in the final drive and led to problems with the bearings. That is why the quantity was reduced. Later the FD was slightly redesigned and the "new one" can be identified by the drain screw on the bottom of the FD.

So there was a problem. Yes. However the "old" FD could be overhauled which is very difficult on the newer version (as per what an expert told me ...).

Brgds from Germany
Oliver

[deilenberger]

The breather may not necessarily be a plus. A friend, who lives at sea level at the shore had a problem with the speed/ABS sensor in his 2012 R12R. When the dealer took out the sensor, for some reason they also drained the oil. It came out milky.

His bike never went into water. It had been a demo bike at the dealership - the service records indicated the 600 mile service included the called for rear drive oil change. The sensor failure occurred at about 6,000 miles.

The dealership was concerned enough to get permission (and reimbursement) from BMW-Motorrad to open the rear drive to inspect it inside. All was fine inside, so it got new oil and he has the bike back.

Question is - how did moisture get into the drive to cause the oil to come out milky looking? On older BMW rear drives this wasn't unknown, especially on bikes that weren't used a lot. The expansion and contraction of the air in the rear drive with temperature changes is enough to draw air into the drive through the vent. If that air happens to be moist air, some of the moisture condenses on the cool walls of the rear drive and eventually mixes with and contaminates the oil. A bike that is used regularly heats up the rear drive enough to evaporate the moisture off. His bike being a demo often sat outside in all weather at the dealership, and didn't get a lot of miles put on it. He also hasn't been using the bike a bunch, and has done no long trips on it (which would help heat up the rear drive to drive out the moisture.)

My bike - which has the sealed rear drive - and also gets very regular use (11,000 miles + every year I've owned it) - the oil that comes out of the rear drive at 24,000 mile intervals looks exactly like the oil I'm putting in it. No sign of any contamination at all. BMW, when the sealed rear drive was introduced, claimed it was sealed to prevent exactly this sort of contamination of the oil and allow for a "lifetime" fill. It seems to work. So - it's a double-edged sword with the vent IMHO. It *may* prevent some cases of seal leakage (or not) but it also does allow contamination of the oil meaning you darn well better do the 12,000 mile changes BMW calls for.

I think the best of the rear drives was the 2nd generation which was still "sealed" - but had a drain at the bottom making it much easier to change the oil. Happily - all the R1200R drives (AFAIK) have the longer end-bearing on the main shaft that was introduced with the '07 model year. I believe that change, plus the lower oil level, along iwth the 600 mile service requirement contribute to the longevity of the R12R drives. So far I can't recall of hearing of one failing (could be.. but I don't remember it.)

[mogu83]

I've always thought there was a pressure build up problem in the sealed drive and mentioned it back in 07/08 when we were seeing seal failures. I recently picked up a 2010 rear drive with the vent and will run it this summer. This bike is the perfect bike, for me, and I get a warm fuzzy feeling when on a road trip except for the rear drive. I've had both the inner and outer seals go while I was on the road, usually after a long run on a hot day. Seeing as all my prior shaft drive bikes have had a vent in the rear drive I don't anticipate any problems with this one.

I do however note that the newer GS bikes don't have the vent equipped rear drives.

[omg1010]

Hi Don,

I think the possibility of "water" entering the FD through the vent is pretty slim. Contaminated Air (humid) maybe, but the possible amount of water contained in humid air will be pretty small and will not lead to milky oil. AFAIK the bearings in the FD are sealed bearings and it may well be that a seal was not in order and that grease contaminated the oil and led to different coloring ... Just a guess ...

Again AFAIK there have been no reports on water contamination in the updated version of the FD.

Brgds
Oliver

[tinytrains]

I live 3 miles from the beach and my K75 (which is vented) has never had contamination on the rear drive oil. Of course it has always been garaged.

Perhaps someone pressure washed the bike at some point in history.

[David R]

I just changed my 12 camhead rear drive oil at 6,000 miles. It was grey, not from moisture but contamination. Small stuff on the
magnet but nothing major. I changed it now and will again when the rear tire is worn out in less than 1,000 miles.
I will keep changing it until the oil comes out like I poured it in.

180cc =180 ml = 6 ounces.

David

[Don C]

There was some gray color in the first lube that I drained from my 2007 bikes rear drive. I think its just assembly lube. The lube came out perfectly clean on the second change, 12k later.

[motoracer8]

I have a 08 R12R with 30,000 miles on it with no final drive issues, I've ridden it to Arizona twice and incountered 110 deg temps. After the 600 mile service I changed the final oil a couple of times with the engine oil, And like Don say's, the oil comes out like it went in.

I have a R75/6 with 170,000 miles on it and the only issue I've had is I wore out the drive splines on the ring gear and had to have them repaired. I replaced the seals when I had it apart but there was no leakage up to that point.

I've used Mobil 1 75/90 in the /6 for the past 20 years and the R1200 from about 6,000 miles.