sound coming from back off car

I have a 96 mustang Gt 5 speed and theres a weird sound coming from the back i think its a u-joint but it really dosnt vibrate when driving and the sound normaly happens when starting out in 1st going around a conner

What does it sound like? Make a squealing sound because you are giving it too much gas and spinning the back tires going around a turn in 1st? Does it make kind of a metal on metal growling noise? If thats the case you could check the fluid level in your rearend. You should just be able to touch the fluid from the fill hole on the tip of your finger. There are tons of noises that can be made. Could be growling because of a bad bearing. A bearing will end up seizing and braking something. Give us some more info if I havent already answered your question.