i have a 2000 5.3ltr x-cab silverado 4x4 and the rear end slips
sometimes on takeoff. it makes a rubbing sound and you can feel
the rear end hesitate. i think it might be the u joint but i am
not sure. I was wondering if anyone has an idea what it sounds
like to them or anyone that has had this kind of problem. Thanks.

 

I recently had the same problem and it was in fact the U-joints. Mine was covered under warranty, but the dealer should fix your problem.

 

Not sure what your problem might me...but according to the manual the rear axle grease does not need to be changed unless you do heavy towing. My dealer strongly disagrees and recommends that the rear axle grease be changed every 30,000 miles using only the GM synthetic lubricant and adds the friction additive for the limited slip differentials. Don't use any other synthetic rear axles greases...they will cause problems. The one that GM uses is made my Eaton...and is similar to the quality used in semis. Alot of people are trying to get away with using the cheaper Valvoline or Mobil 1 synthetic...a big mistake.

 

i had a mechnic change my rear end in my 04 4wd silverado with the auto locker. he used 90 weight oil and it killed the new rear end it may have been shipping fluid, they are realy stupid also have your locker checked if you have one