D
dlearl476
Guest
There are a few problems with your hypothesis - although in the absence of facts - it's probably as good as any..
Point taken, absence of facts.
- The drives which were repaired with new bearings were not hexhead drives. So far - in every case I've heard of - BMW replaces the new style drive as a unit. If there is a problem with shimming variances - it's coming right from the factory (which is likely a subcontractor - Getrag or ZF.) I think it's important to note that the design of the hexhead/new-K drives is really completely different from the older oilhead/K drives. AFAIK - not a single part is shared between them, including bearings, seals, casing, etc.
I based that bit on posts here, that owners had had repairs made with the same shims used.
- The story I heard - which was from a source that claimed they heard it from BMW - but I can't be certain it's entirely accurate - is the reason the oil is being changed at 600 miles is it may have some contamination left from the original machining process. I can't think of any reason to use any sort of break-in oil on a gearbox that has gears and bearings - "break-in" of either of these implies wear - and that's exactly what isn't needed or wanted.
Simply passing on what the dealer told me yesterday. I'm no engineer, but a "break-in" oil makes sense to me. Something to "bed in" new parts, then get rid of the swarf. Triumph uses a dino, no friction modifier/surfacant additives added, "break in" oil in their engines for the first 600 miles. Helps in seating rings and such. I can see it helping to "finish" (polish) gear surfaces and bearings and get rid of machine tool marks but, once again, I'm no engineer.