My car just started clunking when i take off in 1st!

[OrangeMustangGt]

ok guys i need some help. When i take off in first, under say 1/2 or more throttle sometimes there will be a loud "clunk" from the rear end area.! it dosent do it in any other gears, or when shifting, and driving, etc.
Now, i jacked up the car, and i felt the ujoints, they seem pretty tight..i rebuilt them probably a year ago.. I just rebuilt my tranny, so this leaves the rear end, however i cannot duplicate the sound with the rear end jacked up? i was thinking spider gears, but before i pull off the diff cover, i was wondering if anyone has had a similar problem, and where to look? i was thinking something possibly with the rear suspension? anyhow, if i DO need spiders, where can i order then from? thanks guys
as a side note, i did just lower the car, but i cant see anything that is hitting, bacause it makes a pretty pronounced thud, like sorta a deep sound! please help!

 

[94TURBO5 O]

Check your upper control arm bushings.

 

[MysteryMachine]

dude your cars not used to being all the same color lol. It went to hell after you painted it up make it 10 different colors again and it will be fine

 

[donkey_punch]

check your rear sway bar. i broke mine right in between the 2 bolts on the driver side. and would get a loud clunk when taking off hard, and when making sharp turns. for a while i couldn't figure it out, and even gave the sway bar a nice tug a couple of times. and it felt soild. until one day i gave it a gorilla tug and it moved just slightly. i couldn't tell it was broken till i unbolted. cause it broken in between the 2 bolts on one side. so one bolt was still holding it in place.

 

[broken_joke]

my car is making a similar noise. so i jacked the front of the car . pulled the emergency brake up as high as i could. i grabbed the driveshaft and turned it. there was so much slop in the rearend. i told a mechanic friend and he said to take it easy and get it in the shop asap.