From:	Apfelthaler, Horst
Sent:	Donnerstag, 13. September 2001 10:29
To:	'BMW E21 Digest'
Subject:	Switching ring and pinion
Hello,

>In my opinion, the 3:64 is a nice choice.
>[DuckRyder]

>Only 3:45 I have is an open, but if you are unable to find a 3:45 LS, then
>switching the ring and pinion should be possible.

>Robert

just an info how to switch ring and pinion for the case you don't find the right diff:

I did it on my LSD as LSDs are VERY rare in Europe...

- Look for a diff with the correct ratio - this diff has to be used as base for the LSD project.
- remove rear cover and notice the teeth clearence (wording?)!
- disassable both diffs - remove only the LSD unit and the open part - don't touch the pinion part!
- remove the ring(s) and install the LSD unit again in the original housing with all bolts from
  the bearings torqued to specs 
- remember the torque to move the LSD unit
- install the LSD unit in the new housing and play around with spacers to get again the
  correct torque to move the unit.
- install ring on LSD and install it in the new housing
- you now have to take care that you get the same teeth clearance like you had
  in the original diff (typically 0.08 - 0.12mm) by moving the whole LDS unit either to the
  right or left side. - You have to play around with the spacers but you have to use
  the same amount of spacers all the time (one side less - other side more spacer...)
- I did this using 0.1mm paper - finally after have the right measures for the spacers it
  went to a machine shop and hade thicker spacers shaved off.
- mine had originally 1.6 and 1.8mm spacers installed, after switching I installed both 1.7mm spacers

The whole procedure took me about 3 hours - I'm no certified mechanic engineer - I'm computer
specialist...
Diff is running well - no whining, no noise,...

Btw I'm running a 3.64 now (2.7l i-engine with E30 tranny) - maybe I'll switch back to 3.9 during
winter months.

rgds


Horst
http://silverstone.fortunecity.com/chicane/541/