8jest - try a search on this forum, or Google for final drive rebuilding - there have been a few threads
From memory most have not addressed replacement of the bronze spacer between the bevel and the either needle or taper roller bearing on the drive side.
The spacer sets the mesh of the pinion and bevel gears, so it is nice to have it is close as possible.
These bronze spacers are available in 0.1 mm (4 thou) increments from 2.5 to 3.5mm?, so if the dimension of the existing isnt an even 0.1mm a new spacer at least the next size up is required- mine was 0.127" thick so I replaced it with a 0.130" (3.3mm) one, which I think will be close.
This of course means a couple of orders, first after strip down for a bearing, spacer, gasket and seal, then for the correct shims after you have measured clearance with the new spacer fitted - the big shims are $12- each so ordering a selection isnt really an option.
I was quoted $280- for replacing the large bearing , spacer and seal , included resetting the pinion to the correct mesh and reshimming the bearing.
If there is a next time I will let them do it - list on parts is more than half of that, and measuring the mesh and bearing preload for the taper bearing or clearance for the needle roller is hit or miss without the correct equipment.
The drive I just pulled had 8 thou preload on the needle roller even with a spacer worn 3 thou so it was probably assembled with around 12 thou preload instead of zero, FWIW around the error you would expect if you measure the clearance by crushing a few strips of solder, as suggested some places.
And also just about as bad as the factory built the Oilhead drives, but that is another , long, long, story.
Adelaide Hills, Australia. 93 R100 GS, 77 R75/7 ,70 BSA B44VS, , 86 R80 G/S PD, 95 BMW Funduro F650 ST