A Guide to the Hexhead/Camhead Final Drive and Shaft Drive

[krazyhank]

A great write up. Thanks for taking the time to do this. I agree most failures are seal failures leading to bearing or final drive gear failure. The biggest problem is it’s just a poor design. Flat face bearings are designed for a parallel or flat load. That’s why most wheels have 2 bearings to spread the load over a large area. Bikes like a BMW and Ducati use a single load bearing. Imagine the considerable lateral loads on these bearings. A conical shaped bearing, like in a headstock would be better but it would be so large the wheel hub would be massive. Just my 2 cents

[kthutchinson]

The number of splines (20 or 22) that the OP refers to in his original post are on the transmission end of the driveshaft, no the final drive end. For reference, look at the descriptions of the rebuildable driveshafts on Ted Porter's website.

[rtkarl]

Just doing some research here:

My 2017 1200RT with 55k miles had a drive shaft failure. I noticed a new vibration and after a couple of short rides it got worse.

I drained the FD, it had about 280ml of oil (from the BMW shop), I believe that it only takes 180ml.
I then pulled the shaft and fount the front U-joint was obviously failing.

I went to the BMW shop and found that the drive shaft had changed to a Prop Shaft with a new part number, and the price was $219.00 USD.

So, buying a new OEM was the way to go for me.

Karl

[AntonLargiader]

...I agree most failures are seal failures leading to bearing or final drive gear failure. ..

Agreeing with whom? I fix a lot of these and its clear to me that the failure originates in the main bearing. It wasn't completely clear to me until the vented FDs came out, though. Then it was super obvious. The cover is too tight and takes all of the needed clearance out of the bearing. I doubt there is much lateral load. And tapered bearings are not too big to fit in there... BMW did that without making the unit bigger.

Just doing some research here:

My 2017 1200RT with 55k miles had a drive shaft failure. ..l

This has nothing at all to do with Hexhead/Camhead FDs.

[GSAddict]

Here's some additional detail on the chronology of final drives. It's specific to the R1200ST (my bike), but should apply to other models.

There have been five versions of the final drive: two for bikes with Gen 1 IABS and three for bikes with Gen 2.

2005 and 2006 Models, IABS Gen 1:
The original final drive has been superseded by a version with the drain plug added.

2007 Models, IABS Gen 2:
The original final drive was superseded by a version with the drain plug added, which in turn has been superseded by the version with the vent and revised main bearing placement.

So if you're looking to replace the complete final drive with a new unit, only the final Gen 1 or Gen 2 versions above are currently available. But if you're looking for replacement parts and have Gen 2 brakes, you have two choices depending on whether your final drive is vented or not.

Further to that,
The crown gear slots for the ABS sensor are different between IABS Gen 1 and IABS Gen 2.
The Gen 2 FD cannot be retrofitted into a Gen 1 bike.