This might be a dumb question. Some viscous limited slip differentials have a silicone fluid in the LSD friction plate unit that is separate from the gear oil that is in the rest of the differential (with seals preventing the LSD unit friction fluid from leaking into the rest of the diff casing). Is this the case with BMW LSDs in the e34 and e32? Specifically the large case 210 units? Or does the gear oil also serve as the friction fluid that becomes more viscous with shear?
They're not sealed so you need a gear oil that has friction modifiers already added or you can get a regular gear oil and add your own friction modifier to suit. In the past I've used Trans-X and the GM additive with good results.
demet
There are three main types of Limited Slip Differential: viscous, clutch, and gear (aka Torsen). The fluid you're asking about is for the viscous type, which BMW only uses in AWD center diffs, as far as I know. BMW rear LSDs are clutch-type. There are also a few aftermarket gear-type out there (Quaife, OS Giken...).
They're clutch types. You need a friction modifier. I used Royal Purple with the friction modifier already added. But you gotta read the back to make sure it's the one with the friction modifier built in.
Thanks for the clarification guys. I don't know why I was thinking they are viscous type (maybe I was confusing them with the e30 ix limited slip diffs).
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