Limited Slip Differential Health

#1

This past weekend we we getting a little inner wheel spin coming out of T8 at Putnam Park. We’re running the rear bar full soft. So we’re wanting to check the health of the LSD. I few posts suggested between 40 to 50lbs break-away is in range. Anyone care to confirm? Are you using the one wheel on the ground, one up in the air method? Testing torque on the axle nut better or a properly torqued lug nut? Thx!

#2

I suspect that a 30mm socket on the axle nut would be most accurate. All the tests I’ve seen were on the right side of the car, left wheel on the ground, in neutral of course.

My LSD seems pretty far gone (major wheelspin if I tighten the rear bar too much) and it breaks away around 40. Planning to do a rebuild here soon.

I think the typical range is 50-mid 60s. I borrowed a unit from a friend from a junkyard car and it clicked off around 63. These were all done with the car stone cold. Not sure what the effects would be of rechecking when car comes off track hot.

#3

How hard/expensive are these to rebuild?

#4

Ask Brendan Digel… He can do them. Pretty good price too.

#5

just checked mine and its at just over 60lbs so not gonna worry about it for now…:slight_smile:

#6

I have about one track weekend and about 220 miles on the diff i just rebuilt.

It measures out to about 48-50ftlbs on a lug nut (no better worse than the axle nut, btw) w/ Redline 75w90 fluid.

While it is lower than some of your measurements, the diff feels MUCH better than it did before. I used to spin a wheel like crazy coming over the hill in T7 at VIRN. That is now completely gone. One of the track days on the diff were also in the rain and i had no trouble w/ wheel spin.

The rebuild was actually pretty easy. Costs about $255 in parts. I’ve posted the parts list here and on bimmerforums before somewhere if one is interested.

Perhaps the lockup will rise as the diff breaks in. The new clutches are now grinding against a fresh surface on the big dogged washer because i flipped it per bimmerworld’s recommendations. The other/old side was roughed up and worn in. I expect as this fresh surface beds in w/ the clutches, it should get grippier.

#7

Thanks for the posts guys. Now I just need some spare time to test our diff and get the car ready for Grattan.