Drivetrain Rear end clunk

So I have an 03 GT, I got this car about a year ago with factory wheels and tires. I wanted to upgrade to a meatier tire because its supercharged and has a 4.10 rear. Got myself some nice new wheels and wider tires for the rear and then all of a sudden when I took it on a joy ride to test out fitment, after about an hour I had some NASTY clunks coming from the rear end anytime I turned at all. Limped it home to find out my diff had a pretty bad leak (also found out my car doesn't have quad shocks with factory upper and lower control arms), wasn't particularly low on fluid but it was certainly leaking. I replaced the diff seal and put the proper amount of Royal Purple fluid (with friction modifier in it) into the rear end. So that fixed the very aggressive clunking whenever I turned going forwards. About 5 months go by with no notable issues but about 2 months ago, I was backing into my driveway and i started hearing and feeling a similar clunking from the rear end; and only when i was turning. This clunk sort of comes with each revolution of the wheel and its a pretty nasty feeling. I must note that i only hear/feel it after I've driven the car around for a significant amount of time and gotten everything up to temperature which leads me to believe its not a mechanical failure, and it only really does it when I am going in reverse generally. Additionally i must note when I am riding the clutch while turning in reverse its not too bad but as soon as the clutch is depressed I can feel the whole rear end sway almost-- terrible feeling! My thoughts are bad rear upper and lower control arm bushings??? Im curious if anyone else has had this issue or has any insight for me; Thanks!

nickyb said:

Ill take a stab at this. You got a 22 year old stang that you've had for just one of the 22 years of its life.
God only knows what abuse it has endured before you adopted her.
If you love her like I do my stang then go ahead and replace the upper and lower bushings with a good quality set,replace the u joints also.
Remove the rear cover again and check the gears and the endplay.
You will be surprised what spending quality time with her will do for you both.

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You're absolutely right! This cars only got 58k original miles so i wouldn't expect any giant mechanical failure, when i replaced the fluid i didn't see anything catastrophic with the spider gears or any metal in the gear oil. Just seeing if somebody could give me a similar experience and point me in the right direction. Gotta do the control arms anyways with the quad shocks being missing.