I have had a recurring problem with my 95 4-runner. It's got 133k on it, v6 auto. I had a big bounce problem with the speedo. It bounced bad enough to knock it out of cruise on the highway. Replaced the cable and housing, and it went away for a while. It came back, with a vengeance. Bounced at low speeds, medium and some high speeds (went away at 60). Cruise would drop out at freeway speeds. The speeds at which bounce happened seemed to vary too. I had a new speedo head installed, replace the cable again, and all was good for about 48 hours. I have a click under the dash, and enough vibration at 50-60 mph to kill cruise. No low speed bounce, but it starts up again at about 40. Another thing I've noticed is a horrible shimmy at about 70. Tires are new(ish), balanced, rotated on time. Alignment is good (got a lifetime Firestone deal) but it only lasts about 2k before it goes out. All front suspension and steering (except shocks) have been replaced. Rear shocks have been done. Speedo shop said they thought I had a vibration coming from the rear. As I mentioned, the wheels all balance properly, and seem to turn true (no wobble to the eye when off the ground). To the best of my knowledge, the beast have never been in an accident.

Anyone have any idea what the problem might be? Axle? Bearings? Me personally? Subtly warped rim? Help.

 

How were the wheels balanced? Did they use a flange on the lug holes or a cone in the center hole? If the later you may want to check this link out. I had the same problem too and getting the wheels balanced correctly with the flange solved my problem.

http://www.gadgetonline.com/vibration.htm