nseoi

tie rods? check play in the rak n pinion. umm... warped disc brakes? did you get NEW tires or just different tires? properly balanced? warped wheel(s)? has the car been wrecked before? take it to a chasis shop

all guesses

lmatt

Switched wheels with another fox body that doesnt have vibration issues. Vibrates without any wheels on the car. It vibrates sitting on jack stands. It doesnt have to even be moving down the road to vibrate. And never been wrecked. Still has the vin stickers on the fenders and hatch.

Portmaster

Check pinion flange with dial indicator. Check trans oil level. If you get some on your finger look for metallic shavings, check pinion play.

lmatt

Transmission has been gone thru, new bearings all thru. Checked the flange with a dial indicator, no problem found. Thanks.

mustangsneverdie

have you checked to make sure all your tires are in balance

Portmaster

Get a transmission yoke from an old driveshaft and remove your driveshaft annd put the yoke in. (make sure the rear of the trans is a little higher than the front) and run it up to speed on the jackstands. If it shakes you will know it's not in the rear. You could slide the transmission out after that and see if it still shakes (manual only) If it still shakes you may want to look at your flywheel and balancer combo. It's just a process of elimination now.