1. Is the vibration occur at a constant speed, acel and/or decal?
2. Does it occur at the same level when the vehicle is in neutral and traveling at the speed of occurance?
3. Does the steering wheel shake or is it a vibration through the whole car?
If the vibration disappears when the vehicle is in neutral....engine (harmonic balancer-likely) or flywheel/tq converter improperly balanced...
Otherwise...bad rims, bad tires (yes even though they have been balanced)....driveshaft or wheel bearings (front or rear) or bent axle. Next step is raise the car up in the air and run the engine (with the wheels off the ground)...if there is vibration...drivetrain/diff/rear wheel bearing/rear wheel/tire....if there is none...front end.
Member: Never trust a person over 40 who drives a Chevy club
Flatheads ain't so bad!
Certified backyard mechanic I & II