When I get moving on the hwy it seems like it really shakes my wife was trying to hold it in place to get it to stop. It doesnt seem like its really loose or anything. Is this a common problem with third gens? is there a way I could fix it?

 

Not that I know of. Make sure all the screws are tight and in place.

JamesC

 

usually at high speeds it is due to a wheel imbalance or driveshaft imbalance.

 

my 85 had a fan that was out of balance and the dash shook really bad above 60-65, changed the fan and it smoothed out. not likely but anythings possible.

 

Mine doesn't shake at all. NO screws holding it down AT ALL....up to 80mph (never gone any faster in my car).

Your problem is most likely caused by an inbalance somewhere, like the tires/fan/etc.

 

Alignment?

 

hell mine shakes at idle. It's my cam tho!

 

I think mine does a little, better yet the vent stuff under the dash pad does i took it off and one sides missing a piece for the vent on the right side, and the middle piece seems loose.

 

A lil while after I bought the car it started doing it.After chasing balance alignment and all kinds of things I found out I neede ball joints.That fixed it.

Years later,Did it again it was an out of balance tire.

Just recently had a leak a plug wouldnt fix and used some of that green slim stuff.It fixed the tire but it settles and causes the tire to be unbalanced.I had to keep it that way for a few months cause I got laid off my job.Had no choice.Bought a new tire and had it rebalanced when I started working again,fixed again.

It could be anything that spins,rotates or has to do with your font end in my opinion.

 

 

Its definitely not normal. I can drive 100 mph+ and my car is solid--not one shake or rattle.
Are all of your screws in place for the dash and are they tight?

 

I drove them when they were new

The dashes shook

There is a wee little brace in the middle of the dash that is supposed to hold all that plastic still.
Hail GM engineers!!!!

If you have a T-top 3rd gen it will be worse, less structural integrity

When I installed my sub frame connectors the dash shakes minimized and so did a bunch of squeaks and rattles

The dash pad screws work their way lose over time as well

Good luck!

 

I drove them brand new as well and didnt have any issues with rattling.

My 1989 IROC I owned 10 years ago was a rattle trap and sounded like it was going to fall apart when you went over any kind of rough road. As I stated above my 1988 IROC is solid as a rock. Hard to say why there would be a variance from one car to another. I agree that T-Tops off less rigidity and convertibles are even worse.