I've been dealing with this for a while now. I don't drive my car on the highway because it's so annoying. When I get my car up to about 50 in any gear there is a strong vibration in the throttle. Feels almost like grinding. I won't do it if i have the pedal pressed. But when I let off it starts. I have checked everything out underneath and replaced the ujoints and balanced the wheels. I'm leaning towards the driveshaft being out of balance. But I'm used to seeing the vibration at higher speeds on these cars. Any help would be appreciated.

 

its most likely the driveshaft. Checkout all the bushings in the car, really go over everything well.

 

The older f-bodies (below 98) had unbalanced steel shafts. Mine was bad over 70 mph. Maybe it's that or a bushing. Not really sure how you check it. You can tell if it's aluminum with a magnet. If the magnet sticks its the steel one and not the good aluminum type.

Hal

 

its a steel one but i'll go over everything again and get the driveshaft balanced. Opti finally died tonight so I get to do that now. thanks for the advice

 

You may just want to replace the steel shaft with an aluminum one from a LS1. Car-parts.com has them for under $100. I believe they are just a 1998+ front driveshaft (ask others to verify this).

Hal