74 dart vibration problem.

I had a 74 340 Cuda that was internally balanced, and they threw a stock counterweighted balancer on it.......It did EXACTLY what you say.

After nearly pulling my hair out, I crawled under the car and looked with a flashlight (the weight is on the inside)..........and sure enough, there it was............In this case, I simply removed the counterweight (bolted), and got rid of the vast majority of the vibration.

I also had a car that needed a neutral balanced converter, and they put a new one on that was weighted..........Did the same thing..........A friend ground off the counterweight, and again, the vast majority of the vibration was gone.

You read about these vibrations constantly on these forums, and the majority of them seem to be an incorrect balancer or an incorrect converter, a counterweight being the culprit or the missing ingredient.