New (Used) Differential install problems

[John W]

About a month and a half ago, my differential started making terrible noises. Finally got a used small case unit and put it in today. I went for a test drive. The 1/4 mile -- all at low speeds -- was fine. Then it started making noise. Then I remembered I forgot to fully tighten the rear diff mount bolt. I managed to get it home and loosened the four nuts that join the diff to the driveshaft. Then I tightened the diff mount nut/bolt. Then I retightened the four nuts to the drive shaft. The noise still persists. Any ideas? I think it may just be out of alignment somehow ... at least I hope that's all it is.

[cabin]

Probably a stupid question, but you did remember to put fresh fluid in it right?

Also, it would be pretty difficult to have it aligned incorrectly if the 4 bolts attaching it to the subframe are all in correctly.  They pretty much determine the alignment of the diff.

I would go back and check the torque on every bolt again, and make sure everything is where it needs to be and nothing is binding.