Hi Henry. I have some experience of this as I changed Zebedee’s Differential (E30 Torsen LSD) with an E30 Clutch LSD unit about 18 months ago. I searched on bimmerfoums for E30 Differential rebuilds and found a lot of information. Remember the MCoupe uses the same E30 internals and casing. Only the rear cover is different.
So…..I STRONGLY suggest a visit to the bimmerdiffs.com website. Jonathan Thayer is very well known in MCoupe community and offers parts and ‘how to’ instructions for Differential rebuilds. I purchased new LSD clutch plates (including an extra disc to replace the spacer, which gives you 40% lock vs 25% standard) and all the bearings and seals from him. I don’t have an exact number, but I remember parts being around $450. His prices were competitive relative to other suppliers I found.
I found getting the Differential out to be a slow but relatively straightforward process. On the Z3 you have to drop the subframe to get access to the top mount bolts. Getting the Differential apart was easy. Rebuilding the LSD carrier with new clutches was also easy. Just follow Jonathans rebuild guide. In the spirit of disclosure, I’m a bit spoiled as I have a garage, Kwiklift and workbench and did not have to do this is in the driveway…!
My overall rebuild was more complex, as I changed the ratio on the E30 unit from 3.73 to 3.46. The new ring and pinion gear meant that backlash and pre-load had to be reset. I read up on how to do this, but felt it was beyond me. I paid $300 to the ‘Rear End Shop’ in Santa Rosa to have them do the rebuild (remove old bearings, press new bearings, set tolerances..) There is a ‘Rear End Shop’ in the Bay area as well.
18 months and many events later, I’m really happy with the set-up. Wishing you good luck!