How to Assess The Condition of A Used LSD?

[bmwman91]

I am replacing my old small-case 4.10 LSD with something newer and better. The plan is to sell my old one. It has unknown mileage on it since I bought it used a long time ago, and I am wondering about the condition of the bearings and stuff. Are there any relatively easy checks (functional or visual) that I can do to gauge how healthy things are in it? This is mainly because I want to price it fairly and, to an even greater degree, make sure that I don't accidentally stick another E30'er with a dud.

How difficult is it to get the bearings out for a visual inspection? Assuming it is DIY'able, would it be worth it to replace the bearings and stuff prior to sale?

Thanks!

[jlevie]

If the differential is still in the car and isn't making noises (whining or clunks) you can assume that the bearings, ring, and pinion gear are in decent condition. It is also possible to check how much torque is required to cause the limited slip clutches to slip, which say how worn they are.

If you open up a differential and tear it down to inspect the bearings you are out of the DIY world. At that point you'd have to go through all of the procedures for setting clearances (with shims) that is required when rebuilding a differential. And that means special tools and expertise that a DIY'er isn't likely to have.

The output shaft seals can be replaced pretty easily and that won't affect the internals of the differential. Replacing the input shaft seal is a bit more complicated. But unless the seals are leaking pretty badly there is no reason to do so.

[bmwman91]

Thanks. Sounds like it'll be an as-is sale. I do get a fair amount of noise (whining and grinding) from the drivetrain, but it seems to be somewhat dependent on which gear I am in so that makes me think that the transmission the culprit (and Getrag trannies are notorious for crazy noises with lightweight flywheels...which my 11lb M20 flywheel counts as lol).

Once I swap in my new diff, I'll see what changes and go from there.