Maybe a dumb question, but do they? I keep leaving a one-tire-fire in the driveway of a certain few R3v members every time I back out, and I'm wondering if it's my LSD that's shot or if they just don't work when turning the other way. Thanks guys.
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AFAIK BMW LSDs are one-way, meaning they work on acceleration only, not deceleration (or acceleration in reverse). Your LSD should act very little when you are coasting so you can get around corners well, it only tries to lock up when you apply forward torque.
If you had a 2-way LSD it would work in reverse.
I have noticed after a rain spinout (I was testing the LSD out :p) that when I got on it in reverse only one tire spun, wasn't surprising at all to me since I already thought they were 1-way.paint sucksComment
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mine works in reverse... but then again it is a viscous coupling :)Comment
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once I got stuck in the snow and when I would reverse only one tire would spin at a time.
7speedshop.comComment
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hmmmm... 2 say yes and 2 say no. This is getting interesting.Comment
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My understanding of the limited slip assembly in a BMW is the following:
The system is always locked (@ 25%) via a set of clutch packs. When you take a turn one clutch pack or the other with start slipping allowing one wheel to turn faster than the other.
Some reasons I can see it not working are:
1. if you are backing up a steep driveway, there will be next to no weight on the wheels but a high demand for grip, if this situation passes the 25% tolerance of the clutch packs, one wheel will slip.
2. Your clutch packs are generally worn out. Going forward you have the entire weight of the car pushing down on the rear wheels giving you more natural grip, hence why an open diff can leave 2 tire marks when peeling out.
3. Jesus doesn't like you :-(
anyways, clutch packs are cheap and seem fairly easy to install.
JulienComment
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This.Originally posted by Julien View Post
It's a very steep driveway, with no room to get a 'running start' at it. Literally throw it in to reverse and start up a 20% hill for about 15 feet.
Oddly enough though, it doesn't seem to happen in my 325iS or Kennys 318iS. Or even the e34 525iA, which I doubt has an lsd.
the plot thickens...
This one is also true.Originally posted by Julien View PostComment
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They don't. The idea is that they ramp up the locking force (ever heard of ramp rates?) as you ramp up the forward torque, and the force levels off at a certain locking coefficient (typically 25% for factory BMW diffs, however ours are worn out and exhibit closer to 10%). There is probably preload, but when you are coasting there is little locking force, and when you're applying reverse torque through the drivetrain there should be next to none.Originally posted by Julien View Postpaint sucksComment
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Stock LSDs are 2 way
Status: HG repair. 488wtq though!Comment
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Well, that shut me up. Haha.Originally posted by shiboujin View Post
Open diffs can leave two tire marks, it really depends on how even the load is between the two tires. My guess is the LSD isn't working very well in reverse up a hill since there's very little load on your rear tires, effectively meaning there's very little ramp engagement. LSDs work on a load basis.paint sucksComment
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If you want proof, here's me at a drift day.
The first corner you hear my rpms drop, then I let the clutch out quickly. For a second the tires lock up in deceleration, then I power out. 2 way.
Status: HG repair. 488wtq though!Comment
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it is two way. hints how it has a percentage lockup on accel and decelsigpicComment
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