rear end trouble/noise

I just had the stock rear end rebuilt on my 75 not too long ago. Nothing special done just pretty much stock. After about 1000 miles, I started to hear a repetitive clunking (not too loud) when going around a fairly tight long sweeping turn, and it stops once I'm going straight. It also happens (much louder and faster) sometimes when I accelerate from a dead stop into a turn. It has 2.73s and I haven't tried to burn out or load it up real heavy from a dead stop or anything crazy.

Right now I'm waiting to hear from the rear end shop as to what they think it is. Any ideas out there?

I'm hoping its just some posi clutch chatter and not anything too serious.

Sounds like hammering clutches, drain the fluid add 2 bottles of additive and fill up again, do some figure 8s and see if that helps

is there an easy way to drain it without removing the rear end since there isn't a drain plug?

Yes, suck it out.

Sounds like posi hammer as well. Yours is a good example of a question I've been getting for years, "Why is a custom diff worth more compared to the common rebuilds?"
I would ask your shop how the posi was set up and what type of clutches were used. I'm willing to bet that it was a standard build which means they installed a master kit and clutches and that's it. The posi spider backlash is important and if set too tight with those damm springs it will hammer on you.
There should have been additive used(GM) during assembly but who knows what you got unless they tell you. Many times cheaper parts are used in those $600-$800 rebuilds and the end result sometimes are problems.
good luck with this and see how the shop responds. Hopefully the GM additive will work,use Lucas 85-140 gear oil as well.

I got it back from the shop and this is what happened.

They took it for a drive and said it was the same thing as you guys (hammering clutches). The guy went to check the fluid level and it was way too high.

I thought about it and apparently I pulled a bit of a knucklehead move and filled up the diff with only the rear on jack stands. I'm not sure why i did that because when I did the transmission I made sure the thing was level before I filled it.

So he drained it to the right level and put another bottle of additive in, and that was all he charged me for (the additive that is). Also, he said it should go away after normal driving now. He told me what he did when the rebuild was done originally and he did use the additive during assembly.

That being said. I have put about 200 miles on it since then, and its better, but it is still there sometimes.

The clutche faces will wear a little, more so with the springs applying constant pressure. If you still have the problem of hammering,just start from scratch this time, suck out the old oil(unless they tapped a drain) add the Lucas and 2 bottles of GM additive and see how it is. Did he tell you which type of clutches they used?