I took the cover off to replace the fluid in the rear diff and I noticed there were some indentions in the grooves I just want to know if it's normal or if it should be replaced. At the bottom of the groove you can see metal that looks like it was crushed

 

Not sure what you're asking?

Looks OK to me. Kinda typical high-mileage gears.

If it doesn't whine or rumble or anything, and if you didn't see metal chips or powder laying in the bottom of it, and the fluid was still more or less OK but just old, just put in new and run it. I'd recommend 75W-90 Mobil 1.

 

I don't see any thing wrong with it.

 

Alright thanks!

 

Did you find any broken parts or debris in there when you drained the fluid?
Does it make noise as in clunking or howling wgile driving?

After destroying MANY 10 bolts since 1989 yours looks fully operational by the pics..

 

Yes I've worn out several. They go to popping and other sorts of whining racket. Yours looks ok. I've got some extra non-posi rears around in good shape if you needed one. Broke 2 ten bolts with my last T/A then went to a 9 bolt and didn't have problems. May try to find another one when I put my 350 in.

 

I build 8.8 rears to avoid 99.9% of the rear axle blues....