Expert: Roland Finston - 1/14/2012

Question
I have replaced the shocks, struts, tie rod ends, sway bar bushings, and the drive axles. It still shimmies between 20 and 40 during light acceleration or deceleration. The vibration is intermittent but frequent. Vibration occurs at virtually any speed-in town and on highways but is not constant just very frequent, almost like something is out of phase and then in phase but there is no rhythm to the coming and going of the vibration. Even on smooth highways (between bumps) the vibration is like riding on railroad tracks. Wheels have been balanced. Alignment done and rechecked.

Answer
I would check for whether the tire/wheel combination of each wheel is out of round, radially. Either could be slightly off, and by shifting the wheel to a different position on the wheel studs (two studs over) improve the situation, and if that doesn't work by shifting the position of the tire on the wheel (a tire shop would have to do that). You can jack up each wheel after driving a short distance, let it relax for a few minutes, then rotate it while holding the tip of a rod near the center tread and observe whether amount of variation to be no more than 1/16 inch. Lateral wobble measured on the edge of the tire should be less than 2 mm (about 1/12 inch). Another possibility is a bad wheel bearing. These are not adjustable but check to see the amount of end play.