VLSD Failure? AKA The Clunk From Hell

[beaconhillkilla]

I've posted about this a few times over the past year. The rear end of my car clunks like hell whenever the car is under heavy load. This can be when I have anyone sitting in the back seats, I'm driving up a hill or any time I try to shift hard.

At a stop light and I want to drop the clutch? Noooo. The next thing I know my car is clunking so bad it sounds like it's going to blow up. It's also gotten to the point where my car is a two seater. Any time I have any weight in the back and do anything other than granny shift it the car will clunk.

I've replaced:
-Rear differential bushings
-Installed some subframe lockdown bolts
-Trailing arm bushings
-T shaped differential subframe bushings (outrigger bushings)

I also have:
-Polyurethane motor mounts
-Group N transmission mount
-Polyurethane pitch stop
-The whole set of shifter bushings

And:
-Both rear struts are only three years old
-I've had people move around in the back while I've driven and it seems like things are better when someone sits on the left side instead of the right.

I'm at the point where I've throw enough money at bushings to rule them out. The ONLY thing I can think of is that the VSLD is dead. I don't know how the hell the thing works, but my understanding is that when it's under heavy load it does its magic and makes the car slip less. Well, maybe that magic has run out. I have no idea how many miles are on it. I just needed a 3.9 diff when I swapped trannys and that's what went in.

Thoughts?

Thanks.

[RoughDiamond]

I have the same heart-beaking sound from my under side. Only on hard load, but around corners too. I don't really hear it when I take off in a straight line.

However, I also have blown rear struts and a few bushing that are bad. I'm not ruling out a dead/worn VLSD (@ 193K, I wouldn't be surprised) but it almost sounds like it's coming from the T-case. I can't exactly pin it down to the rear...

I know I also have some tired U-joints, so I'm also thinking those could be a culprit as well (since I have the 4EAT, I only load up the rear on hard accel/slip).

[Legacy777]

Have you had the car on jacks and tried rotating the rear wheels to see if you feel any binding or other weirdness?

[jefferson]

You might try swapping out the whole diff for a different one and see what happens then. Someone on here should have one.

[rallyak]

I know you've changed some bushings but no mention of the outrigger bushing. I've had issues with mine in the past and sounds exactly what mine was doing. I did change mine but that's not why it was making noise, it was the bracket that you bolt on was bent. I did it from jacking the car right on the bracket. I would check it before you pull the diff out.

[RoughDiamond]

While doing the lateral arm bushings, I found that one of my axles make a HELL of a noise when I try to rotate the diff... It seems as though I have a binding when I force the other wheel to turn compared to just letting the diff pick which one. It's also an aftermarket axle, replaced some unknown time ago..

[beaconhillkilla]

Have you had the car on jacks and tried rotating the rear wheels to see if you feel any binding or other weirdness?

I've had the car up and had the whole rear end out at least twice since I started having this problem. I haven't noticed anything in my time working on things.

[beaconhillkilla]

I know you've changed some bushings but no mention of the outrigger bushing. I've had issues with mine in the past and sounds exactly what mine was doing. I did change mine but that's not why it was making noise, it was the bracket that you bolt on was bent. I did it from jacking the car right on the bracket. I would check it before you pull the diff out.

These have also been swapped out.

[beaconhillkilla]

While doing the lateral arm bushings, I found that one of my axles make a HELL of a noise when I try to rotate the diff... It seems as though I have a binding when I force the other wheel to turn compared to just letting the diff pick which one. It's also an aftermarket axle, replaced some unknown time ago..

I thought about this too, so I pulled off both axles and checked them. Everything seemed okay.

[zeke]

My 90 wagon would do this I changed the transmission fluid with redline gl-5 75w90 and a lubeguard lsd friction modifier and the problem never came back