My 94 Cutlass Cierra drives smooth until 60 mph. From 60-65mph you start feeling a slight vibration. At 65 the vibration is getting worse and by 70 the steering wheel, dash, everything is vibrating. Back down to 60mph and everything is fine.
Have replaced:
1. All four tires
2. All four shocks
3. Four wheel alignment
4. Spark plugs and wires
5. Upper motor mount- dog bone

Have noticed one interesting thing. The car pulls to the right yet there is no abnormal tire wear.
Could it be the main motor mounts?

I don't know if CV joints could cause that kind of problem, but it does sound like the problem is associated with front suspension. I have experienced the same type of in a Ford 4WD pickup and the problem was caused by worn out bushings in the track bar.

First thing to check is wheel balancing, from there, I might suspect a worn wheel bearing assembly on the right side. Are all your suspension items such as tie rods and balls joints been greased recently? I would recheck your work, as the only thing that would cause a vibration that severe is usually the wheels being that far out of balance. -Chris

Its your half shafts or the harmonic balancer. Good luck.

My 94 Cutlass Cierra drives smooth until 60 mph. From 60-65mph you start feeling a slight vibration. At 65 the vibration is getting worse and by 70 the steering wheel, dash, everything is vibrating. Back down to 60mph and everything is fine.
Have replaced:
1. All four tires
2. All four shocks
3. Four wheel alignment
4. Spark plugs and wires
5. Upper motor mount- dog bone

Have noticed one interesting thing. The car pulls to the right yet there is no abnormal tire wear.
Could it be the main motor mounts?

I have the exact same car, and mine does the same. If you find out why let me know!

if it's a 3.3 liter, I'd suspect the balancer. If it's a 3.1 or 2.2, I'd look for a bent rim or bd hub bearing. One other thing, check the brakes. IF the rotors are worn uneven, it can cause a vibration like an out of balance wheel. My 91 cavalier had exactly the same symptoms, changed the pads and rotors, vibration gone. They didn't look that bad either, but it was time to change the pads anyway, and since I had it torn down, I replaced the rotors and vibration went away.