I recently swapped out my original open rear-end carrier with a used posi carrier. I am not sure what year it is from but it is an 8.2 like the stock one. 2 questions, I have it in now and drove it tonight but I notice awhat sounds like gear noise that was not there before. Could it be because the ring and pinon are not meshing exactly the same as before? I had to shim it a little different than it was,( all I changed was the carrier I kept the same ring and pinon) or the other thing I noticed when I put the axles back in is it seemed to need a little help to get the 4 bolts that hold the axle in, almost as if the axles were meeting some resistance in the posi carrier. Does anyone have any knowledge in this area? Thanks

You need to set up the pinion angle and depth. Did you use a new crush sleeve?

Could be that the races and bearings are bad. You really need a very clean environment when changing out.

I did not even take out the pinon gear, I just took the ring gear of the open carrier and put it on the posi unit. I pressed new bearings all around and set the back lash at around 8 thousands.

Pretty sure you need to recheck pinion angle and depth when you swap out carriers.

Yes I did that, I put the marker grease on it and checked the wear pattern and I got it very close to what it was before bot I guess it would not have to be off much to make any noise right?

Pinion depth will stay the same when swapping out carriers. Pinion depth will stay the same in any differential housing. They are set up from the factory to have a 'prescribed' pinion depth. It sounds like the used carrier might have issues. I would go back in and recheck lash now that it has been run.

Also, make sure you use the GM additive for the posi. DO NOT use synthetic gear oil. It's too thin for the older units.

I did use the synthetic oil I was told it was better, what is the correct back lash for the gears?

How much preload do the side bearings have? Did you check the pattern and lash in at least four places around the ring gear? When you say it needed a little help to get the four bolts in, what "help" was needed?

Always try the axles in the splines of the replacement carrier before assembly. It sounds like you have/had tight splines. Use regular 80-90 gear oil. .008 lash is good. I usually shoot for .005.