Join Date: Jun 2002
Location: The Deep South of Vermont
Re: measuring final dirve preload (yet again)
Many posts exist in the archives here which answer the questions raised.
In summary: Plasti-Gauge is not suitable in this application; read pasts post for a discussion of why.
Other "crush" methods using solder or epoxy have been discussed, proposed, or tried. Dan Martin is the only person I know of who has written about his results using epoxy. To my knowledge, no one has provided data comparing one of these methods to another known method that would demonstrate consistent results on multiple final drives. Because of a lack of data I would not recommend using any of these methods.
I have compared results using the dial indicator method first described by DMAN to results using the method described in the BMW Service Manual. Both these methods are somewhat technique sensitive but will provide consistent results in experienced hands. The DMAN dial indicator method is a little more forgiving and is probably a better method for someone who is planning on doing just one drive. However, the DMAN method can be misleading, and the process of measuring should be repeated several times to ensure that consistent results are obtained.
On cleaning the pinion shaft assembly: Disassembly of the pinion shaft is not for the faint of heart. Special tools, high torque values, ability to heat the whole drive housing are required. Unless there is reason to disassemble the input pinion assembly (e.g. "creeping needle bearing race) I recommend against disassembly.
Using a parts washer with clean solvent, flush the pinion shaft assembly area while rotating the shaft as thoroughly as possible. In my experience, not a lot of metal gets into this area. After running the rebuilt final drive a few hundred miles, I recommend changing the lube again to flush out any residual solvent; rarely has residual metal been seen or reported.
Last edited by CharlieVT; Jul 21st, 2012 at 5:54 am.