Leaky seals/ final drive

[fratedog]

Looking for for some intel on why for the second time in less than 2 years, I get seepage of oil from the bellows area (particularly on the wheel side, down the triangle connector to the para-lever). Bike is a 2004 R1150R, with less than 25,000 miles on it. All maintenance complied with along with an additional 2 drains and checking of final drive oil for contaminants... none found. Seals were replaced both times. The only thing I've noticed on this R bike compared to others (2) I've had, is after a good couple of hours of spirited mountain riding the housing of the final drive is quite hot to the touch. I've heard some BMW seals are inferior?? Perhaps a higher grade/quality? Any other suggestions,comments or ideas greatly appreciated. Cheers, fratedog

[towerworker]

What seals are you replacing? The "bellows" you refer to--are you talking about the black rubber dust boot or CV boot as is on most cars? The drive shaft housing is a dry housing. It's not unusual to have a bit of a leak there--at least both my '03 and '04 both do. One small drop of oil will look like a big problem because of all the dust and grime it seems to attract.

[bransan]

Fratedog, this is a normal occurrence on this bike. I have 60k on My 04' purchased new. I have changed the final drive fluid every other oil change. Never saw any metal fillings or other contaminants, and always a good quality oil. I just wipe off the oily dirt once in awhile and call it normal. I also have had the bike disassembled twice, by Myself to perform the clutch spline shaft lube. There has always been a little oily residue associated with that end the bike.

[johngellis]

Maybe just a coincidence but mine leaked since purchased with 2k miles. At 16k I changed transmission and final drive oil with "racing" synthetic I purchased from Boneyard. At about 25k the final drive stopped leaking and hasn't leaked since. It has about 36k now. Magic.

[riceburner]

The theory I heard (and subscribe to) is that he gearbox oputput shaft seal is 'just above' the top level of gearbox oil, so even when it does start to leak, there's only going to be a trace amount that escapes from the gearbox. It tends to run down the shaft in the (dry) tunnel, and end up leaking from the bellows. It looks worse than it is because of the dust that gets caught there.

My bike is on 91,000+ miles now, afaik the gearbox output shaft seal has never been changed*, it leaks, and I've never had any gearbox oil issues. (I'll admit the gearchange is getting notchy, so it's due a tear down and inspection by someone who knows what they're doing, but the oil changes have shown no issues at all).




* I had most of the bearings in the gearbox changed, so the seal may have been changed then - not totally sure, would have to look up the records.

[fratedog]

Good stuff... thanks guys, I have heard that the tranny output seal could be the culprit way back when. Just my old tired brain forgot to remember. Going to my wrench for troubleshooting and will try to post the solution or more mystery. Cheers, fratedog

[duegi]

Over filling the transmission with too much gear lube will also cause this sort of fluid drainage. I filled my transmission up too much a couple of times with a little bit of gear lube trying to push back out of the filler hole while I was putting the plug back into the transmission. A week later I had some drainage coming out of the FD side bellows of the drive line. This continued until the gear lube fluid level in the transmission equalized or reach a happy point.

Since I've used .83-.84 of a qt. to fill the transmission and no further drainage issues. To be sure what was leaking I used different color (brands) of gear lube to differentiate where the fluid was coming from.

I still run different fluids in both to keep track of what is going on with the transmission (Mobile-amber) and FD (Belray-red).
Also don't be shy about changing the fluids regularly (5K) as it's cheap compared to a rebuild or breakdown away from home.

[Arbreacames]

It could be a tranny leak, but FD leaks might be more common. The problem at the FD is that there are several unusual paths through which the FD oil can leak that are unrelated to the input shaft seal. In the drawing below, the input shaft seal (joint #4) would be responsible for preventing leaks along paths B and C. To prevent leaks along paths A, D and E, it is necessary to use the correct sealant. I can see how a mechanic could miss the importance of sealing these metal-to-metal interfaces correctly.
According to the charismatic but OCD-prone French engineer Isatis (http://isatis.mecanique.free.fr/K1/Join ... nt/p5.html), Hylomar sealant is specified at A, and Loctite 2701 at E. I have had success with the Loctite grey gasket maker throughout the assembly.

[bransan]

Thank You Carlos. That is a great drawing.
I can see clearly now.
Next time I do a spline shaft lube I'll be looking into the final drive leak.
I never worry too much about it, it's never all over the wheel or even very low at the change interval.
A minor seep in the grand scheme of all things mechanical.