Many things cause vibrations

Question:

I have a 1972 Cadillac Coupe Deville with the 472 cid engine and three-speed automatic transmission. The car has something between a vibration and a shake at certain speeds. It’s not bad but it is aggravating.

The ball joints check out OK and I had the A frame bushings and the strut rod bushings replaced as needed. I also had the steering center link replaced. The car has new brakes, tires and shocks. I had the wheels balanced twice on different machines and the drive shaft was completely rebuilt with new Spicer U-joints and then it was machine balanced. I visually checked the harmonic balancer and don’t see any wobble.

I can feel the shake or vibration in both the seat and steering wheel. Any help would be greatly appreciated as I’m out of ideas.

Answer:

A wide variety of different things can cause a vibration in a car. A defective or incorrectly adjusted wheel bearing can be the cause. A bad engine or transmission mount or malady in the differential can also be responsible. An imbalance in the engine could be the culprit and this could be due to a mechanical imbalance in the reciprocating assembly or to an imbalance in the running of the engine, such as occurs when there’s a misfire. The vibration can be in the transmission, torque converter, or flex plate. It can also be caused by any component that’s attached to the engine, including the alternator, air conditioning compressor, or power steering pump being loose.