Once I get over about 80mph I can feel/hear a vibration coming from under my car. If I keep my foot on the gas while slowing down it isn't noticible, it's much more obvious when I just let off the gas and coast, or pull the car into neutral. Is this my driveshaft? Just hope it's not the rearend....

 

Probably the driveshaft/tires/axles.

 

I'm about to get new tires, so if that doesn't solve the problem could I assume it's the driveshaft? Would an aluminum DS fix the problem? I'm eventually going to get 4.10's, so wouldn't it be an good idea anyway?

 

Do a search on this subject. You may find a good solution. For me, it was turning my driveshaft 180 degrees on my rear yoke.

Ben

 

My car was vibrating real bad and i had the tires balanced. Made a world of difference.