hey guys just trying to get a little info. I have a 1994 camaro z28. My issue is on the freeway at around 70mphs my car starts to vibrate pretty bad. Its bad enough that my passenger seat has begun to come loose and wiggles while im driving and my dash starts to rattle as well. The car has a fairly new tranny mount do you think its motor mounts? everything on the car is stock I have not begun to mod yet if that helps. Thanks for your info guys its greatly appreciated

 

Motor mounts could be the cause, but check your tires to see if they have "chord shift". I'm having my rear tires and wheels checked because I get annoying vibrations at varied hwy speeds. I've tried different tires, so I'm thinking it's my cheepie chrome wheels that aren't very true.
When going slow (10 mph) does your car seem to sway or wiggle side to side?

 

no not at all what does chord shift look like? or is that something a shop has to look at. My two front tires are fairly new and my passenger rear is pretty new and my driver rear is bald i haven't had the time to get a new one do you think that could be causing the issue? on the street i see no problems but once i get on the freeway and hit about 67 and up it starts to shake pretty bad.

 

Chord shift is visible when you jack up the rear wheels and start the car, the tire will look warped as it goes around, either side to side or in height. The other way to tell is what I mentioned before about the car wiggling side to side when going slow.
Another cause could be u-joints. If the u-joints are a little bad and your motor mounts are bad too, they can kinda work together to cause a vibration. Also, a weight could have flung off the driveshaft.

 

Well first I would definitely get that tire replaced. Then maybe get an alignment, just to be sure. You might have the dreaded driveshaft vibration (though I haven't heard of it vibrating seats loose!) that comes with the stock driveshaft. The vibration usually starts at around 85 or 90 mph, but it could definitely be sooner. But I would get that tire taken care of first. My buddy drove on a bald tire and it went out on him, tore up half his fender and bumper when he went off the road!

 

Transmission mount??? Do you have a steel drive shaft???? There were problems in the early year of being off balance......

 

whatever came stock as for the driveshaft because it has not been changed. Im definitely getting the tire taken care of asap.