Output drive shaft from the differential on Rod change type gearboxes,the teeth very rarely wear badly but the side cover bushes(2A3538)sometimes ruin the shaft causing those dreaded oil leaks from the seals in the output covers CHM85.these wre £139-00 retail
Two of these main diff carrying bearings are required in the gearbox and this new steel caged type fits either way round--The 3/4" width outer track type had a side marked "thrust side" which must face away from the gearbox. These usually shim up at 4 thou pre load as opposed to the very early non thrust type bearings which were 1-2 thou.
Genuine Rover are now 48 thou thick which is so tight they can lock up your differential. The originals were .035 thou. These are machined down to be exactly the correct size required but we also stock oversize 43 thou type which are available as BTA102 for worn units. We have never required anything larger that was servicable.
The latest model Mini differential still use thrust washers on the spider gears but now have a tab on one end to prevent them from rotating on the cage side of the diff. The cage of course is cast while the gear itself is much harder and thus the whole assembly now lasts much longer. Check the casing seating where these sit for deep scratches where poor...