Thanks for the info. (archive)

I'll post a followup sometime when I actually get this done. I have ordered the parts, and will rebuild it when my transmission clutch wears out (any day now), and I have to pull the driveshaft anyway. I'm not going to get into machining parts to make a custom setup. But it sounds like the lockup percentage is related to the clamping pressure and frictional forces in the clutch "pack". I'll see what I can do to tighten it up.....maybe some shims?

In the meantime, I'll just keep the diff topped off (she's leaking).

Other than thick clutch discs, are there any tricks I should know about to increase the lockup percentage of my LSD. I'd like to shoot for 50%. Are there thicker springs, or shims? I've never rebuilt an LSD...my only experience is rebuilding an American open diff which was pretty easy.

Any help would be appreciated

You can increase the lockup by putting in your new clutch discs with the old ones so the stack will be even thicker. I don't have the article handy, but remember something like this:
The diff has two sets of clutch and spring discs on each side of the axle gears for about 25% lockup. Putting in three sets is good for about 40% and four will give about 60%, or something like that...

Anyone have the real data??

You only have so much room to work with inside the differential casing, so it's not as easy as just dropping in extra clutches. You also need to have an equal number of clutches on either side of the spider gear carrier or you'll have on wheel that slips much more easily than the other. To get another set of clutches in you'd have to have allmost 4mm of material machined off either the spider gear carrier, diff unit housing or it's cover on either side. BTW, for the '77 model year only, BMW offered a 40% limited slip differential that only had one set of clutches per side, but the locking mechanism is different in those as is didn't use springs to compress the clutches.

FWIW,

Matt
Maximillian Importing

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