Differential & drive shaft rebuild

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    Henry Loh

    Hey folks! It’s TIME!

    The title says it. Having replaced the CSB and all rear bushings and wheel bearings, I’m still getting tons of rolling noises and vibrations, with a nasty grinding noise in slow turns. Time to rebuild while I have access to a driveway and my tools.

    I’m going you ask can help me with making a shipping last and game plan for this.

    Drive shaft is easy – pet per Ryan Rich’s and Kolesars recommendation, I’ll be bringing that to South Bay Driveline.

    What about rebuilding the LSD? Bearings definitely need replacing, clutches, other bits?

    I’m also taking volunteers to help rebuild it!



    Nigel Mott

    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!

    Henry Loh

    Sweet! Thank you!

    I’ve been trying to soak up as much infor as possible reading forum posts and trying to get the shopping list started. Here are a couple threads I’ve found helpful




    Based on the reading I’ve done, I think I will not do the Porsche 2.1mm dogear (apparently this will increase preload and can shorten the live of the internals). I plan on removing the 4mm spacer to add an extra dog ear and clutch disc to up the lockup.


    Howdy Henry

    This is a pretty ambitious project. Even when I was into 4x4s (Jeeps & Toyotas) I left any messing of the internals to a competent machine shop/transmission specialist. I never felt comfortable, nor did I have the proper tools to shim, set backlash, and pinion depths (preload) to spec. I have to agree with Nigel on this one. Infact, I think anytime you remove the carrier (ring gear) you should always check tolerances.

    Of the three hyper links you posted this one is the proper method. The other two simply replace clutch packs and then re-install without properly setting everything back into position.


    You can probably get away with these other method since your only putting down 160 horse power & Torque.

    If you want my .02 cents. I would drop the pumpkin and have the guts re-freshed at a transmission shop or speed shop.



    Now am going to get long winded here. I think the reason you set these items to tolerance is for optimal performance. It’s set to lock up at just the right moment when the car needs it. If the ring gear, clutches, and pinion are not working in harmony the rear may lock up to early or too late or too abruptly and actually slow you down.

    Someone please correct me if I am wrong.


    Henry Loh

    Awesome feedback! Setting those values was also a concern of mine. If I can find someone with experience dissecting diffs to help me out, I’m willing to give it a shot. If not, I’ll ‘pay the man his myoney’!



    PS: It’s a 1991 318is – I WISH it was 160 hp!!!!

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