Differential lock-up test

[JGood]

Did the diff lockup test last night on my e30's. I used a recently calibrated torque wrench, with a socket on the hub nut. The test wheel was up the in the air, the opposite wheel was on the ground. Car in neutral, no e-brake.


87 325is track car - 52 lb/ft

85 325e daily - 30 lb/ft


Both diffs are 3.73 LSD's. The 87 track car has 270k miles on the diff, the 85 325e has a diff out of my friends wrecked 110k mile 87 325is.

The whole reason I did the test was because the 325e one-legs badly.

Would a fluid change with Redline help? Or should I not waste the money on the fluid and pick up another diff?

[whiltebeitel]

According to Ranger1 on Bimmerforums, he said that 30 lb/ft breakaway at the rear wheel bearing nut is the lower limit for the factory spec. 65 lb/ft is the max allowable for Spec E30.

But I don't think the fluid would make a very large difference.

[Dave]

Factory 3 has a clutch pack kit. Get that and some new seals . . .

[FredK]

Don't people add half Redline NS and half Redline with slip additive to get a little more lock?

Thanks for that idea, Dave. Maybe I'll open up the diff for fun this winter. :D

[JGood]

Yeah, I don't know about tearing into the diff...

[Wh33lhop]

Don't people add half Redline NS and half Redline with slip additive to get a little more lock?

Thanks for that idea, Dave. Maybe I'll open up the diff for fun this winter. :D

You can do that, or just use NS and get the additive separately. But from what I understand this is more of a band-aid as opposed to new clutch packs. Mega hardcore status if you tear it up and grind down the ramps for shallower angles :p

[lifeiskaos]

having never done this before, what exactly happened at 52 ft/lb and 30 ft/lb?

[jlevie]

The point of this test is to find out how much torque is required to cause the clutches in the LSD to slip. You use a torque wrench to measure the torque that you are applying to the axle nut. If using a clicker style torque wrench you find the point that the wrench doesn't click and turns the wheel.

A change of fluid can help a worn limited slip differential, but it is no substitute for replacing the clutches. It is quite easy to replace the clutches on an E30 differential. The parts and procedure can be had from Factory 3 Performance

[JGood]

It is quite easy to replace the clutches on an E30 differential. The parts and procedure can be had from Factory 3 Performance

Thanks, I'll check it out. I was under the impression that it was very involved.