screeching rear end

[95RoushV6]

I actually own a 95 3.8L Mustang, but I have a rear end from a '99 GT in it. For the last couple of months I would occasionally hear a screaching/grinding sound coming from my rear end while I'm accelerating or driving over dips in the road. I'm posting now because over the past week it has gotten really noticeable. Any ideas? I can't really discern whether it's my suspension or if it's coming from the differential.

 

[trombonedemon]

Need to check brake pads and or get underneath the car to see if you can see rubbing spots, anything that was welded that has broken loose.

 

[95RoushV6]

well it happens when the rear end is under load, it wouldn't be low differential fluid or anything would it?

 

[txredgt]

Can you see any residue on the cover or have the gears been changed out recently? Why does it have a rear end out of a 99?

 

[trombonedemon]

well it happens when the rear end is under load, it wouldn't be low differential fluid or anything would it?

Look for some oil stains around the diff. cover and the back of the "pumpkin." If you have oil leaking from the driveshaft area, you need a diff. seal and the vent for the diff. housing might be clop, which would cause the seal to blow. Its very possible you too much play in where your pinion meets your gear, it could also be you need new U-joints.
Clunks are somewhat hard to find without regular maintenance for a vehicle by the original owner.
My lower control arms clunk sometimes (after market). My T45 transmission clunks. On take off, underload, the top of the diff. housing could be hitting the rubber stop (bad springs). Could also be upper control arms bushings, gone bad. Sounds are hard to diagnose over the internet.