Mustang Vibration Problem

[Wayne Maybury]

I have a fully restored '66 Mustang 289 (slightly modified), automatic, PS, PB, etc. It is a nice daily driver but it has a vibration that I have not been able to track down until now. The steering wheel doesn't vibrate so it must be coming from the rear of the car.

I had the wheels balanced a couple of times, I had the drive shaft balanced, and I changed both U joints. The vibration is at it's worst at just around 65 mph, especially if I do not press hard or remove my foot totally from the gas pedal (that is I gently press and release the pressure on the pedal). I haven't gone over 70 with it due to this vibration so I cannot say if gets worse or is less at higher speeds.

I have Cragar SS wheels so the suspicion was that the wheels are causing the vibration due to the oval wheel stud holes. I decided to try removing the rear wheels one at a time and moving them by one stud to see if this changes anything. While doing that I noticed that the left rear wheel bearing appears to have some movement or slack in it. I can move the left tire and wheel between an 1/8" and a 1/4" while the right wheel tire does not move at all.

While there is no apparant wheel bearing noise, I do not like this slack so I am going to order 2 new wheel bearings and seals. Would this cause a vibration at highway speeds? Any other ideas? I love my Cragar SS wheels so please don't tell me to get rid of them.

Wayne