Driveshaft/transmission

[rlaird]

My ride is a 1982 R100RT. My problem deals with the drive shaft. The oil in the drive shaft transfers into the transmission. This seems to happen rather quickly but I can’t tell you mileage. I can tell you for sure that when I’m on a trip every morning I have to refill the driveshaft. In the past this used to happen but into the rear differential. I had the seals replaced than it started to do it into the transmission. I suspect I have to replace the seal into the transmission but am I missing something. I don’t see a vent for the driveshaft but both the transmission and differential have one and I checked them and they appear to be ok. Can I replace this seal without opening up the transmission? My Clymer manual says I have to move the whole engine/transmission unit forward before I can get the transmission out. Is this true? I can’t find any leaks and when I remove the level plug on the transmission its apparent the oil is ending up there. 44,000 miles. Thanks

[rlaird]

Another question. I'm from Milwaukee Wiconsin any recommended place to take the transmission

[20774]

The bolt that holds the lower end of the speedo cable to the transmission has a hole down the middle and allows the tranny to vent. Remove this bolt and run a fine wire through the middle. Then reinstall the bolt. Be careful of the torque...it doesn't have to be that tight.

I'd say do it with the bolt in place, but then you might end up pushing some gunk into the tranny...not good.

Maybe that will help.

[crazydrummerdude]

You can remove the transmission by taking out the swingarm bolts and taking the transmission out the back. This is the only method I've used, so I can't speak for whether or not it's easier than the other.

Also, I've got old leaky bikes, but I almost never have to worry about the oil (loss) in the driveshaft area.

According to your story: How does the oil in the driveshaft get into the transmission? Then how does that not cause an overflow in the transmission when you check it?

[rlaird]

The extra oil does come out of the level plug in the transmission.
I have removed the bolt and checked it.

[88bmwJeff]

You said you had the seals replaced. Was that in the final drive only? I've read that if the seal at the back of the transmission is installed backwards, oil can migrate. If you didn't need replace that seal, then it sounds like that seals ready to be replaced.

[20774]

How full are you filling the driveshaft? I believe the manual calls for 150cc but in reality about 100cc will do. There really is no good way to try and use a dipstick method to determine the right amount of oil. The shaft itself is in the way...I recall the dumb way that my Clymers shows how to measure it. Eventually, I just drain and put back in a measured 100cc.

I'm also wondering why the oil is migrating that direction. Oil doesn't run uphill and unless the rear shocks are completely sacked, I wouldn't think that the oil could get into the tranny. Unless there's too much and/or quite a bit of expansion.

I can't recall the situation with a v-notch at the output area of the tranny, at the 12 o'clock position. IIRC, there isn't supposed to be an opening there, hence the breather bolt. If you have an opening, the heating/cooling cycles could be drawing the driveshaft oil into the tranny...

[rlaird]

Only the seals in the final drive were replaced. At that time it wasn't going into transmission.
Rear shocks are ok and were replaced while this was going on. The front springs may be a different story
I suspect that BMW expects the oil to migrate forward. I understand the reason for the oil is to lube the universal joint and perhaps the slider on the differential end. This would also explain the seal and the rubber boot that leaks if not properly installed or cracks. I don't know if the seal is installed backwards on the transmission.
If I drain the driveshaft it is almost empty so it doesn't appear to be seeking
100cc but rather going to empty.
I do find it "interesting" that the oil just seems to want to leave.
I assume that the rubber boot is expected to swell or contract rather than have a vent for the driveshaft.

[kstoo]

Another question. I'm from Milwaukee Wiconsin any recommended place to take the transmission

Glen Bishop at Thoroughbred Cycles (http://www.thoroughbred-cycles.com/) my favorite.

Matt Quirck at MotorWest (http://www.motorwestmotorcycles.com/) I haven't been here yet but I have had nothing but good report.

[20774]

I recall recently in an old MOA News reading about some kind of "fix" that was needed for the early /5 models due to large changes in air volume. I believe that a small hole with tube was poked through the top part of the bellows to relieve the pressure. Maybe that has something to do with the appearance or disappearance of the vent in the rear seal of the transmission. I wish I could remember those details.

[AnnapolisAirhead]

I read a response from Oak to a question about how much oil to put in the shaft. Let me see if I can recall it reasonably correctly.

Like someone said here, 100-125ml (or cc, same thing). Do not overfill it--that's when things go bad. The only time you would ever put in 150ml is you have had the shaft removed from the bike and were therefore cerain it was completely emptied.

The oil should settle at the rear of the shaft near the pinion but it can run forward too depending on how the bike is stored, two-up, luggage, etc or anything else that would affect the angle of the drive shaft. If it runs forward, quite a bit can rest in the shaft boot. It doesn't need a whole lot and is apparently not all that critical (unless its bone dry I suppose).

Crazydrummer mentioned taking out the swingarm nuts to back it out. That would give you a good idea where its going...and you'd know the shaft is completely emptied at that point. Getting the boot on is kinda 'fun'.

[lostboy]

There is a seal at the gearbox output shaft which is supposed to prevent the transfer of the driveshaft oil into the gearbox. Yours has probably given up. The gearbox will need to be removed but there is no need to disassemble it. Whoever is replacing the seal will have to use special tools to remove and retorque the flange; there is no getting around the special tools in this case.

The seal is intended to be installed inverted; the garter and lip will face out. There is a very small triangular opening at the top of the seal. This is the vent for the driveshaft. Don't be tempted to close it.