loud gear whine after install on decel

I had razors edge a local shop in S. FLa do the install. I first purchased a used set of gears that after 10 hrs of install time they found that the ring gear was slightly warped. purchased new Precision gearset and still a real bad whine and chatter. Said screw it and decided to put in a new Dif while we were in there since the old one had 160k on it and was real loose. after 8 more hours of adjusting it still is real loud on decel. at around 3k. I watched them prestty close and I dont think they used anyhing but trial and error with the shims to get the teeth lined up. at this point I am considering takeing it elsewhere because I am over a grand in parts and labor and still no satisfacion although they said to bring it back to see if they can correct it. On them of course. real nice people who do some wicked engine work. You can catch them in the next issue of race magazine. I just want a rearend that makes no or very little noise. I dont think they used any friction modifier.

is there anything I should tell them to make sure to do on their next attempt to make it work?

one final question. Is there anything I should ask to make sure they do no what they are doing?

friction modifier was used. baclash was .011. a perfect rectangle in marking paste. all in spec. I am leaning toward a bad set of gears as well. It will be in the shop tomarow for what i am sure will be another 8-10 hours. Could the crush sleave be a possible solution? It wasnt loud at all and then one down shift and wheeerrrrrrrr!!!!! I say this because the sound wasn't pressant at first but showed up later from one down shift.

:worship: You are my hero! that sight is great!! cant wait until tomarow to see how they look once opened. I realy appreciate all the help from all of you. thanks again. and again.