If you’re already rebuilding your BMW’s differential, eEuroparts has developed a kit to upgrade your BMW E36 LSD unit. This is key for any BMW seeing track or autocross duty.
From the factory, E36 BMWs that were equipped with a limited-slip differential (LSD) came with a 2-clutch LSD. This literally means there were 2 clutch plates in the LSD. These LSDs are also called 25% lockup as when one wheel slips, up to 25% of that torque gets transferred to the non-slipping wheel. If your inside rear tire is spinning in tight corners (as ours was), transferring more of that torque to the tire with traction means faster lap times (as our upgraded diff did).
Back when BMW was making these 2-clutch, 25% lockup LSDs, Porsche was equipping many of its cars with the identical LSD unit – inside of different differential housings – BUT, the sporty Porsches came with 3 clutches, offering a 40% lockup. Spoiler alert: the BMW LSDs were built to accept 3 clutches. If you haven’t figured it out yet, we’re going to pull the spacer out of the stock BMW E36 LSD and replace it with an extra set of friction material to get your BMW putting more power to the ground than you thought was possible! As a bonus, this is a great opportunity to replace your existing friction material with fresh plates and disks, as these are wear parts after all.
Read below to see just how easy it is to perform the 3-clutch upgrade to your BMW diff:
- See our other DIY that describes how to remove the differential from the vehicle and the LSD unit from the differential.
- Make a clean workspace for yourself (dollar store table cloths work great for this) and set the LSD unit on it, bolt side up.
- In a clean container, soak the new LSD clutch plates in differential fluid. Do this for a least 30 min. Just like a motorcycle clutch, NEVER put in a multi-plate wet clutch dry. We also put in the dog ear plates just to keep all the new parts separate from the old ones.
- Working in a star pattern, gradually loosen the carrier cap bolts. Unfortunately, these bolts are notorious for stripping, as the head of one of ours did. The eEuroparts kit includes stronger 12.9 replacement bolts.
- After the 8 bolts are removed, carefully remove the LSD carrier cap and set it aside. Note that inside the cap may be one or two washers, pull those out and set them aside, keeping them in order.
- One at a time, pull out each part of the LSD unit, cleaning them with a lint-free rag and setting them in order. There is one clutch disc flanking each side of the geared center of the LSD.
- Toward the bottom of the BMW E36 LSD, there is a large spacer that we will remove and replace with the 3rd clutch disc. It’s a good idea to measure this spacer to make sure it is 4mm thick – exactly the width of the new clutch friction disc and its accompanying dog ear plate. Remove the spacer.
- Note that the new clutch disc and dog ear plate will not take the exact place of the spacer – they will be situated next to the existing clutch and dog ear plate below the spider gear assembly. Thus when reassembling the BMW E36 LSD it should be the 3 small washers first, the large-diameter Belleville spring (cone-shaped washer) and then the 2 pairs of clutch and dog ear plates.
- Reassemble the rest of the diff in reverse order – making sure to lightly coat each part with diff fluid first. And of course, don’t forget to swap in your last new clutch and dog ear plates on the top side of the spider gear assembly. The LSD unit cap will not fit flush due to the inherent spring tension of the unit.
- Finger tighten the 8 bolts securing the LSD unit cap. Then, in an alternating star pattern, tighten each bolt ¼ turn, slowly cinching down the cap. Not doing this will put undue stress on the cap – increasing the chance of damaging it. This will take some time, be patient!
- For extra credit, once the cap is fully tightened, remove one bolt at a time to put blue Loctite threadlocker on it. Individually Remove, Reinstall, and Torque each of the bolts (again, in a star pattern) to 30ft-lb.
- Return the LSD unit to the differential as described here: https://www.eeuroparts.com/blog/10763/whats-the-diff-bmw-e36-differential-rebuild-diy/
The hardest part of this upgrade is just keeping the parts in order. Otherwise BMW made this very easy by basically making an upgrade-ready diff for us. It really is that easy to have the best LSD of your life…
Here’s the list of parts used:
8x M8x16 Carrier cap bolts 33147740005 (eEuroparts upgraded 12.9 bolts are 91290A418)
3x LSD clutch plates 92833255100
3x LSD dog ear plates 91733255211