Forum bmwbike.com

How does the R51/2 driveshaft differ from the R51/3? Are they interchangable? Is the Mobile Tradition/Huggett new production driveshaft assembly an exact duplicate of OEM?

This is an interesting one Stephen.

The BMW parts list shows the R51/2 shaft as No.30 38 026 and the R51/3 as No.30 38 027

The difference might be at the pinion end where a felt seal is listed for the /2 and a lip seal for the /3, therefore the sealing surface might be of slightly different diameter between the two. The illustrations are no help as both look identical but I guess a /3 would fit a /2 with a suitable modification to the sealing arrangement.

Stephen,

One difference between the two is where the white rubber dust cover rides on the driveshaft. The R51/3 has a recess machined in the shaft the dust cover sits in. This prevents the dust cover from moving forward on the driveshaft. The R51/2 driveshaft does not have a recess. I think they may be the same except for this one difference.