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My Final Drive puked all over my rear wheel!


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Hmmnnnnn . . . . When I washed my 1150GS after my Baja trip last week, there was all sorts of goo on the drive side of my rear wheel. I washed and dried the bike and then I pulled the wheel to verify that it was final drive lube. It was.


The level was about 2 ounces low in the final drive, that's about 25 perecent lost. I could see where it leaked out around the crown bearing/seal. I ran the bike with no rear wheel, and could feel no knocking or clunking at all, so I believe the bearing is probably OK. I ran it up to speed in 6th gear for a while and no more oil came out. I filled it back up to the bottom of the fill hole threads with Redline Lightweight Shockproof as is my custom and I guess I'll just keep riding it until something breaks.


BMW says in their manual that the final drive can leak oil while in use due to some kind of a "suction effect" if the final drive is laid on it's side with oil in it. I must admit that my bike spent a little time on it's side on this ride (more than once actually), so that may be the cause.


Anyone have any opinions or experience with this?

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If the bike was down on it's side the gear oil could leak from the vent at the top of the housing.

I would clean it up, refill, and then keep an eye on it.

Sounds like it's nothing to worry about.

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Thanks Tobias, but it didn't come out the vent. It came out of the seal around the hub, where the crown bearing is.


I'm not sweating it, but considering how well everything looks (besides oil leaving out of the final drive, the bearings feel great and no slop when rocking the rear wheel at 3:00 and 9:00, etc . . . .), I just kinda suspect that somebody else must have had this happen.


Then again, maybe not!

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My 1100GS started to leak around the large seal. I was riding the bike on Friday and on Saturday mornin, when I planned to get it out again, there was oil on the garage floor.


I took the old seal out, visually inspected the big bearing and fitted a new seal, added oil to the specs and it was all well 15k km's later, when sold.


So the seal just failed. I guess it was normal, a 1.5$ seal to fail @ 90k km's...



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As Dan said, seals can go.

As you have checked the bearing for collapse or wear and it seems to be good, it is easy to pull the seal. While it is out you can check the state of the rivets in the crown wheel bearing to ensure they have not started to break up.

Pop the new seal in and hopefully good to go for another considerable amount of miles.



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I would replace the main seal in the final drive (very easy), and then just keep an eye on it. If the seal leaked once, that means it is compromised and it WILL leak again at some point. I don't like the idea of gear oil anywhere close to the rubber that keeps my butt attached to the road

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Morning Jonathan


Well you did the right thing by cleaning it up then watching for where the leak is coming from.


A few things that can cause final drive seal leaks are:


-Failed crown bearing (you said yours is OK)


-Plugged vent causing over pressure (anything from external mud to internal bridging from cruddy oil or internal debris)


-Something like a piece of grass or string or who knows worked it’s way under the seal lip.


-Obviously a failed seal


-Rust or corrosion on the spool hub in the seal contact area.


Other places that LOOK like a seal leak are:


-Cover “O” ring leaking


-Loose cover bolts


-The 2 piece hub is seeping between the pressed together joint. (Will be gear oil in center of hub and center of wheel)


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skinny_tom (aka boney)

If you bike spent a little time on it's side, then it's possible the vent got oil in it. If the final drive is hot, or becomes hot shortly thereafter it's possible that the pressure forced oil past the main seal.


After being upright, the oil probably will have drained from the vent allowing it's normal operation.


If you didn't see any signs of failing bearings and it's not leaking now, I'd go with this as "most likely."

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Thanks for the advice and information. If I see any more oil on my wheel, I'll go buy a new seal and change it. Maybe I'll try to clean out the vent while it's off, if I remember. If no more leaks, I'll just keep flogging the poor beast.

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You and the beast looked very happy when you passed Beth and I (we were on the side taking pics) up on Sonora Pass.

Hope you get many more happy miles down the road.


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