Shaft to Final Drive seal

[montmil]

Some months back, I stopped a niggling gear oil drip off the bottom of the final drive case. New O-rings on the rear brake cam shaft fixed it.

This past week, after returning from the Three Sisters jaunt, the rear rim was lightly misted with oil and road dust. A good cleanup took care of that.

Later, I ran through all the fluid checks and found the final drive reservoir to be low. Not dry bones low, but enough to warrant draining and refilling with fresh gear lube. 1981 and later R65s have the shock absorber coupling on the drive shaft and it's all but impossible to check the oil level per the manual. Drain and refill is a much surer lube service. 150cc per the book.

My question is regarding the seal between the driveshaft's rear splines and the final drive. Item #5, I think, on the attached parts image. I'm wondering if the shaft oil is migrating into the final drive and then somehow leeching out in the form of an oily mist. It took nearly 250 miles of "spirited" riding to show up.

http://www.realoem.com/bmw/showparts.do?model=0364&mospid=47851&btnr=33_0619&hg=33&fg=10

I would likely wait until our two-month winter to tear into this. In the meantime, I'm seeking counseling from y'all plus the folks at the Bandera Home for the Bewildered where I am permitted to roam unaccompanied.

Monte

[Bob_Roller]

Your final drive was low on oil, did you drain the shaft housing oil to see about how much was in there ?

First thing I would do, is to remove the rear wheel and look the final drive over, you may have another leak there .

Just a thought from something Sue had happen, the mushroom top vent on the final drive filler had gotten pushed down, preventing the final drive to vent when it got up to operating temperature, may be worth a quick check .

[nhmaf]

Yes - Check your little mushroom-head vent to be certain - if the final drive gets warm enough and no atmospheric venting is available, the increase in pressure inside the final drive can cause gear oil to bleed out of seals it wouldn't normally.  Sue's bike had oil all over the rear wheel from ~ 300 miles of riding on a hot Tennessee day.   After we fixed the vent and replaced the oil we cleaned up the wheel.  Not a drop came out on for the rest of the rally or her trip home, I believe.

But, if that isn't it - I agree with checking, filling, riding, and rechecking the oil quanitites in the final drive and in the drive shaft.  It is possible that you are getting oil migration from driveshaft into final drive, but it gets to be a somewhat 'involved' job pulling things apart to replace the seal between them - best avoided unless you have to.  And, if your final drive was low, but not the driveshaft, then it is not likely that driveshaft seal is leaking.

[montmil]

I checked and adjusted the final drive "mushroom" vent on both R65s when the topic was first posted, so they are OK. No oil film on them, either.

Drained out approx 100cc of gear lube from the drive shaft supply. 150cc is listed as full fill. The final drive was checked before the trip, and after, with lube at correct level both times; just a dribble out of the "level" inspection hole.

I have no drips off the bottom of the final drive housing since replacing the O-rings on the brake cam shaft. I habitually run my finger under the case after almost every ride.

Perhaps the oil mist is from the crankcase. However, the engine is dry and dip stick is at the mid-point where I run it. Maybe getting some oil mist pushed out thru the airbox "duck call" valve. Mine is not in the best of condition. I'll also take a look at the pushrod tube grommets.

Both the transmission drain bolt and the plain bolt that replaced my neutral switch are dry.

Much to do about nothing I'm beginning to think. At least the rear wheel is tidy looking. I'll keep a weather eye on all lube levels.

Let y'all know if I discover anything worthwhile. Thanks,

Monte