1990 GT Vibration at high speeds! Help please...

[jpart5oh]

Hey guys I am new to this things. Just wondering if I can get some input on my problem. This only happens at high speeds I would say probably 70+. Any suggestions/opinions is welcome. Thanks!

 

[jfsram]

I'd start with the easy stuff like wheel balance.

If you have to dig further a super wild guess from WAY over here would be driveshaft.
Without any more details, it's all guessing.

What speed? Does it change downshifting one gear?

 

[wheelhopper]

I agree, start with the easy stuff and work to the more expensive.

Wheel balance
Check play in wheel bearings
Check tie rods
Alignment

 

[vfast]

is the dog bone still in place? what do the universal joints looks like? does it has a squeaking sound when in reverse?

 

[fast_lane]

like the others have said, start with the easy stuff. Try switching out the front a rear tires and see if it makes a difference. While you have the tires off, check the front end for any worn parts.
If the virbration is something new, check the tire air presure, missing wheel balance weights, bent wheel,etc.