This is the first car I have had with a posi unit so I'm thinking that is probably the root of the problem. anyway, the rearend has new shock,springs,rear 1" sway bar and urethane bushing with boxed control arms. The carrier is a rebuilt posi. A friend I work with is an ex-mechanic that had set up rear ends in dozens of new cars. He was meticulous doing this and when I was thinking close enough on the tolerances (backlash) he wouldnt quit until it was right on the money, so I dont think that is the issue. we didnt remove the pinion, just put the old ring gear on the new carrier. anyway on to the problem. I've noticed when I make a hard 90 degree turn into my drive (the drive has a nice little pitch from road to driveway) it makes a popping sound in the rear when I pull into the drive.I can back up and pull forward again and the sound is gone. The only time I hear/feel this is pulling into my driveway.also I dont hear any whinning comming from the rear. I's this something thats normal with posi units or should I start looking for a problem. also I did add the bottle of gm posi fluid to the rear end.

You might try adding more posi oil supplement and see if it stops the popping. However,I wouldn't add more than two bottles. If that doesn't help,you have a problem that needs to be looked into. It definitely sounds like the noise is coming from the posi unit.

I'm not saying this is your problem, but when you change gears is always a good idea to change the ring and pinion. They get worn to each other, so when you only change one of them they won't wear correctly.

Michael,
I think Clint is right on. Go to your local GM dealer and get 2 bottles of posi additive, put them into your unit and go for a ride. Bet it doesn't pop when you get home.
John

A new tight aftermarket posi will probably do exactly what you're hearing. IMHO, it's normal and nothing to worry about. When it's worn out it'll never pop.

It is NOT normal for a rear to "POP" This is definitely an indicator that something is amiss.

Check the manufacturer for their recommendation for what kind of gear oil and additive belongs with this unit, and make sure its full. This can happen sometimes when the unit isnt full.

Does the sound seem like it's transmitted through the frame? Can you feel it through the seat?

This may not be your answer but, the reason I ask is, I had a popping sound that took a while to find the problem.
I had a rear end built by a very reputable shop and I replaced the control arm bushings while I was at it. It would pop turning into my driveway or when you blip the gas going straight.
I took the car back to the shop and had them listen to it and they said they didn't believe the pop was internal. I even went to a Jiffy Lube and crawed into the pit while someone made it pop and couldn't pinpoint the noise. I then started taking the control arms off one at a time to inpect them. Turns out the drivers side upper control arm was slipping off the bushing on the side that's not press fit.
I replaced the control arm and the pop was cured.