Rear end slipping, clunk sounds

[Bo]

Please help! I have a 2001 2500HD 6.6 Duramax 4WD, 131k miles. Rear end seems to bind or lock up then slips when taking off. Bumps almost always from a stop and slips when going into an incline. Rear end fluid is clean and no sign of metal debris. I pull a fairly light trailer (1500 lbs) and it does it with or without the trailer. I bought the truck used about a year ago and this problem is only getting worse.

I have already replaced the brake system and fuel injectors, etc.. on this truck and don't know if I'm fighting a losing battle. Any help is appreciated.

[Mark Rinker]

Doesn't sound good. Have you checked U-joints? How many miles on the truck and how was it used by its previous owner?

[mark45678]

you may be feeling the rear end locker engage and wheel spin ? Its poss it may be just a posi unit locked up and tire scrub , once the lock up it takes a few miles to un lock some times. Almost never hear of any bad 11.5" gm rear ends , it poss ..... injectors are the only issues gm had from 2001~2003 trucks.

[Bo]

It has 131k miles. I bought it off a car lot that I know pretty well when it had about 100k miles. I did run into the guy that owned it before and he said he never really pulled anything with it. He's an older guy and said he just likes to get a new truck when they hit around 100k. Must be nice!

I checked the u-joints just by trying to move them side to side. They seem tight, no play in them. Please keep in mind, I'm not a mechanic. Ive learned a few things over the years but have never owned a diesel. I'm just stumped on this one.

Just one more note: yesterday on the hwy at about 70, my rpms were close to 3k and it just didn't feel right. When I let off the accelerator it seemed to slow down guicker than usual. This morning, same speed, the rpms were at
2kand it felt normal.

[DmaxMaverick]

You may be due for a tranny service. The control main filter (external spin-on), when plugged, will cause all kinds of shifting problems. It will also decrease the available fluid flow/pressure, and can cause serious issues with slippage under load, like accelerating or towing. I'm suprised you aren't limping with DTC's (SES lamp) screaming at you.

[Buck]

It could be the slip yoke needs to be lubed;) There was a TSB waaaay back when....I had the same thing happen when I had my '01 Dmax.