Hi guys , yesterday I lifted my car. Gear on neutral, when tried to rotate one wheel another one didn't rotate right away in same direction then I tried to rotate it faster same thing results even more gap, looks like differential don't lock right away. I have 164k miles on my car , previous owner didn't tell me anything about differential but looks like i have 3.91 gear so i don't know how many miles on it ... I don't exactly know how this should works but I think both wheels should lock and shouldn't be easy rotate them . Mine rotate pretty easy similar on neutral and on first gear. Should I rebuild differential ?
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Last edited by Zezorro; 10-30-2020, 05:31 AM. -
The diff has to sense slippage. This builds pressure inside of the pump in the LSD unit and then presses the clutch pack together locking the wheels.
Normal.
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To give the thread an answer mamatcng the title, the unit is stout and gears can last a very long time with reg oci. It's the lsds that give out after some time after 100k give or take ofc, gradual as well. Car feels less dynamic, less grip on acce/torque while turning. Like driving a non M
DD: /// 2011.5 Jerez/bamboo E90 M3 · DCT · Slicktop · Instagram
/// 2004 Silvergrey M3 · Coupe · 6spd · Slicktop · zero options
More info: https://nam3forum.com/forums/forum/m...os-supersprintComment
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it's a viscous unit though isn't it? that fluid breaks down just like anything else and it requires more and more slip to engage making it less effective. I seem to remember a video about a CSL/6sp conversion that was done at a shop in the UK that specialized in replacement diffs for M cars. I'm sure the race teams weren't using viscous units, there has to be a torsen or clutch type replacement option out there somewhere?Comment
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It is a unique clutch-type design which also features a shear pump.
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I'm no diff expert, but I'm still reading that it depends on the viscous fluid inside that "pump" to engage the clutches.
viscous fluid breaks down and wears out over time. it's "lifetime" just like the service interval of most BMW trans fluid.Comment
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It’s a viscous type diff.
The pump or top plate is lot rebuildable as far as I know. You can get replacement clutches.
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Redline gear oil ruined my first diff.
2nd one has some slop in the spider gears so it’s getting a rebuild with ~ 100k on it. Going to use the gear set from my first diff as there’s no play in it (bearing failure is what happened to it)Comment
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