Transmission oil and Final Drive Oil (again..)

[ca1ic0cat]

I've read the threads on transmission and FD oil weights and called the dealer and what I'm coming up with is confused. I bought the Royal Purple full synthetic 75w-90 for the transmission and Mobil 1 75W-145 for the FD but the dealer is saying 75W-145 for both transmission and FD. The new owner's manual doesn't list the oil for the transmission or FD. The threads seem to be conflicting.

Mine is an '05 GS. I recall my old owner's manual referencing 75W-90 for the transmission but I can't recall.

Does anybody know the latest information on what oil viscosity to use in both? Is the BMW stuff really special?

Thanks,

Eric

[marc]

I think you have it backwards. Ignore your dealer as he seems to be telling you what makes his inventory situation easier, not what your bike needs. For one thing the consensus seems to be that you should NOT use the higher viscosity gear oil in your FD. It just doesn't get all that hot. The higher viscosity MAY be used in your transmission. Some like it, others don't care.

A synthetic 75W-90 (or 80W-90, or straight 90) hypoid gear oil with a GL5 rating will do for your FD. I happen to be using the BMW 75W-90 because that's what I bought a long time ago. You'll get 4 or 5 FD changes from a quart.

You can use the same thing in your transmission. That's what BMW specified and what I used last change. Or you can use the 75W-145.

No, there is nothing special about the BMW labeled stuff.

[scootertrash]

Originally Posted by marc

I think you have it backwards. Ignore your dealer as he seems to be telling you what makes his inventory situation easier, not what your bike needs. For one thing the consensus seems to be that you should NOT use the higher viscosity gear oil in your FD. It just doesn't get all that hot. The higher viscosity MAY be used in your transmission. Some like it, others don't care.

A synthetic 75W-90 (or 80W-90, or straight 90) hypoid gear oil with a GL5 rating will do for your FD. I happen to be using the BMW 75W-90 because that's what I bought a long time ago. You'll get 4 or 5 FD changes from a quart.

You can use the same thing in your transmission. That's what BMW specified and what I used last change. Or you can use the 75W-145.

No, there is nothing special about the BMW labeled stuff.

Actually, my dealer uses the 75W140 (P/N 07510395257) on GS F/Ds. I seem to remember the service manager there telling me that that is what BMW technical support has directed them to do in light of all the FD failures. A directive of that sort, would, of course, supercede what was written in owner's manuals before that.

It's probably worth checking with another dealer for a second opinion.

[marc]

All the FD failures? The most common hexhead failure is a leaky oil seal. That was initially addressed by a change of the oil quantity, not the oil viscosity. Current drives have a vent to make it better, yet. Another failure is the big bearing... it lives on the dry side of the inner oil seal so oil viscosity will have zero bearing () on its life. The pinion bearing is in the oil, but you don't hear of many of failures in that area since BMW went to a larger bearing in '06 or '07, forget which.

There have been no other reports of a viscosity change from BMW, even on the newest, 2011 models. I don't know what your service manager heard.

[ca1ic0cat]

Got the transmission and engine oil changed last night. The bike seems to be happy with both. Did go with the 75w140 in the transmission. This doesn't seem to have affected shifting. No metal in the old oil so all is well.

The FD I'll do next as that's a bit of a project. My FD has been fine.