Grinding noise from rear end = worn spider gears?

I had 4.56 gears put in last week, and since then, in addition to the driveline vibe issues, I have had a strange and rather bad-sounding noise from the rear diff. It's very low-pitched, I can feel it in the floorboards and the steering wheel, and it occurs when I go from accelerating to coasting. When I am accelerating it's quiet, and when I am coasting it's quiet, it only makes noise during the second or two when I transition.

With all four wheels on jackstands, with the XJ running and in gear, the passenger tire spins and the driver's tire remains motionless. When I hit the gas, the grinding noise occurs sporadically, and each time it does, the driver's wheel rotates a little.

I examined my side and spider gears, and it looks like my spider gears are worn out, but is that likely to cause a problem like this? It was fine until I regeared, but the carrier and spider gears shouldn't be turning any faster than they were before at the same speed, correct?

Spider gears only rotate when your cornering.

Sounds like the pinion might be loose.Also,since you never posted back anything different can we assume you are running that horrible pattern that you posted?
http://www.naxja.org/forum/showthread.php?t=954422

RCP Phx said:

Sounds like the pinion might be loose.Also,since you never posted back anything different can we assume you are running that horrible pattern that you posted?
http://www.naxja.org/forum/showthread.php?t=954422

Click to expand...

After the final set-up the pinion turned with 25 in/lb of resistance, so I don't think it's loose.

I'm sorry you think my gear set-up is "horrible," I didn't hear anything like that from you or anyone else when I posted the first time, and the local gear Guru checked it out and said he didn't think I would have any problems with that setup.

I thought you got plenty of feedback!The 8.25 is really hard to get quiet with the best set-up.
You also didnt mention any run-out numbers?What brand gears?Your U-joints may not like the new set-up because of the increased rpm's.

Backlash is .008". The gears are US Gears. My rear DS was rebuilt and rebalanced about 3 months ago. I have an SYE, and I've set the pinion angle properly with angle shims.

I did a bit of work and greased everything this evening, so I will see if it helps any.

Thanks for your help.