Ive been feeling a slight shake that happens only at around 45mph. If I put it in neutral or 3rd it still vibes until I slow down or speed up some. Is this the driveshaft? Is this a suspension problem? As far as I know everything under the car is original. The shocks/struts still feel pretty firm but may need replacing.

85 trans am
LB9
th700r4
3.27 bw rear
"performance suspension"-i dont know if that matters

thanks

 

Usually between 45mph - ~60mph it is yer wheels are outta ballance.

More than likely that is yer problem.

Kat

 

They were supposedly "expertly" balanced at Firestone. I'll take it somewhere else and see if that helps. Ive had MANY problems with Firestone service and all I've had done there is get tires mounted! I guess I like their tires, but hate their service.
thanks for the advice

 

Might be the universal joints on the drive shaft.

 

If you put it in neutral, and it was still vibrating, then it shouldn't be your driveshaft.