dkinzer

I've never had a vehicle with a limited slip diff before so I don't know exactly what I'm seeing or looking for. This is on a 2001 2500 Sport 4x4 automatic with about 45K miles.

I've been noticing lately a groaning sound from the rear end (I think) at low speeds turning sharply - like when pulling to the garage or a parking space. Yesterday, I did an oil change and tire rotation so I put the rear axle up on stands to make the swap go easier. While it was up and the tranny in neutral I tried turning one tire by hand expecting the opposite side to go the other direction as usual. It surprised me by turning the same direction.

I wondered if it might be a limited slip diff so I blocked the opposite tire and found that I couldn't turn the other one by hand. Should I be able to? I checked the diff and found the limited slip tag so that's definitely what I have.

I've seen posts about limited slip clutch chatter. What does that sound like?

I plan to remove the diff cover to see if there's anything visible, e.g. metal particles, etc. Anything else I should look for?

Thanks.

Don in Portland, OR

piperca

"I wondered if it might be a limited slip diff so I blocked the opposite tire and found that I couldn't turn the other one by hand. Should I be able to?"

That's a good question that I'd like to hear the answer to, also.

Recently, I adjusted my rear brakes, jacking up one side at a time to do the adjustment. It was stiff to turn, but I was able to rotate the wheel to adjust the brakes. Now, I am not sure if this is normal. Hopefully someone will chime in and help us both out!

wannadiesel

Sounds like you need some limited slip additive to stop the noise.

A good Powr-Lok diff should not allow you to turn the wheels opposite directions by hand. If you can, the clutch packs are shot.

The official Dodge test for a Powr-Lok is this: Lay a piece of masonite slippery side up on the ground. Put a piece of butcher paper on top of the masonite. Drive one back wheel onto the masonite and paper. Put a 2x4 in front of a front tire. Try to drive over the 2x4. If you can, the diff is OK.

piperca

Not to hijack the thread, but that's not good news! What would have caused the clutch packs to fail? Is it a costly repair? Is it something I can tackle myself?

When I adjusted the brakes, it was done in neutral. I found the following while doing some research myself:

"If your shaft is tight, test the clutch pack as follows: Leaving the vehicle in Park, or in gear, jack up one wheel. Apply a torque wrench to one of the lug nuts and begin to rotate wheel (either direction). A good clutch pack will show at least 50 ft. lbs resistance to turning (read directly from a beam-style wrench, or set a 'click' style to 50 ft. lbs. If it clicks before the wheel rotates, that means at least 50 ft. lbs force). This must be done on each wheel, for there are two clutch packs, and they do wear differently."

Being that I was in neutral, would there be any difference?

wannadiesel

Do the Dodge test before you panic. What I said was they should not turn opposite directions (both wheels off the ground). Yours is probably OK. The Powr-Lok isn't spring loaded like a GM Posi-Traction, it uses the torque of the engine to clamp the clutch packs when there's a load. The clutch plates are dished to provide a little preload, but it's not as tight unloaded as a Posi or a SureGrip type unit.

They wear out due to making tight turns under power, mostly. Two different size tires will tear one up in 100 miles, though.

I rebuilt my Powr-Lok in the driveway by myself. It's a heavy sonofagun, but not too bad a job. The clutch packs will set you back around $50.

piperca

Wannadiesel, I guess I was editing while you were replying. See my previous post.

wannadiesel

You won't be able to turn the wheel without breaking the axle if you test it that way. Where did you get that info?

That could be a valid test with the trans in neutral.

Try the Dodge test. If it'll do that, it's in good shape.

piperca

I found that on some 4X4 site. I went back and checked and they were referring to Dana 44 rear ends on an International Scout. I'll try your method, it sounds less damaging.

dkinzer

It seems to me that the Dodge test that you described will confirm that the clutch packs don't slip too much. A different test would be required to determine if they slip enough. A test like that described by piperca seems to fit that bill. Anyone know if the 50ft-lbs is a reasonable torque?

In a different thread, someone described replacing the diff lube with the type that requires limited slip additive and then doing low speed figure 8's in a parking lot to see how much chatter or tire slip you get. It was suggested to put in small amounts of the additive at a time and repeating the test until you get the feel that you want. The caveat was that if you put in too much you'll get too much slip and you'll have to drain out the lube and start over.

Don