I've been having a vibration since i bought my car and i cannot figure out what's causing it.
It starts around 55-60 Mph and i think is comming from behind, i can feel it in my sit.
the vibration goes away when i take it out of gear, i've already installed a ne suspension Package from Laurel Mustang, its been Aligned, and i still feel the vibration. Any suggestions what is causing it?

Thanks

 

Jack up your car and run it and see if it still vibrates, it could be the U-Joints, or the rear end , the tranny, or even tires out of balance.

 

Not sure what trans you have but c4 or whatever try it at the same speed but in a different gear. (if possible)

If you have a c4 for example lock it into second gear and accelerate to 55 or 60 and see if its any different.

Gun

 

sit in the back seat have someone drive it see if its worse in the back seat or not.

 

Make sure all of the lug nuts are properly attached as well.

 

what rear end?
1)check lugs
2)check u joints
3)this is the bad one, jack the *** end up and pull the diff cover and check your gears.

my bet is on #3

 

probably a stupid comment, but what about the balance of your rear wheels? if they arent balanced you get "speed wobble" at about 50-60mph. stupid suggestion, but its a cheap fix if it works.

 

Thanks for all the Ideas im going to try them and see what happens.

 

could also be bad axle bearings. mine are shot in the II and if i jack up the car i can actually move the wheel up and down a little bit

 

u joints or rear, i used to have the same problem