Noisy final drive post-mortem
Took a few minutes today to dismantle the LC final drive. These are my findings.
BMW have significantly simplified the design. Tapered roller bearings are used on both sides of the shaft to accommodate the axial loads and the casing itself is no longer shimmed. Everything sits in oil bath. Bearing pre-load is set by design and gear clearance might be adjusted by shimming of the bevel gear shaft, I din't dismantle that yet but that seems like the only way of adjusting for correct backlash and teeth meshing. It does not look like there are any spacers used to set the races for correct bearing pre-load.
The wheel side bearing seems too wimpy, the rollers are tiny and judging by common sense to widely spaced, only every other window in the cage is populated. Judging by it's condition and black iron sludge everywhere, this is the bearing that failed and was making noises. The race is scored, wear lines are clearly visible. My guess is that this bearing has a limiting speed that is too low for the application it's put to as smaller rollers have to turn faster for the same angular speed and in effect they work harder.
Bevel gear shaft has two opposed taper roller bearings by the looks of it, they look beefy and should last for ever.
Both gears are in very good condition.
There is no perceivable problem with the bevel gear shaft bearings.
I'll report on all bearing and seal sizes in second part once I get my bearing pullers from the lock-up.
He who laughs last thinks the slowest...
Last edited by beemerbart; 04-Jun-2018 at 03:32 PM (855).