I have a 1996 Ford explorer 4.0L vibrates at 30 MPH. The Vibration happens at 30 MPH and is felt in the steering wheels and seats. I have taken it to three different mechanics. They can not find the problem. They have checked the bushings, front end, & U-joints. All say their fine. The last mechanic told me my tires were chopped and that was the cause of the vibration. I replaced the tires this weekend still vibration. I even had to replace a front right axel. I was driving the truck back from the mechanic, and decide to put the truck into 4X4 and I noticed the vibration was less. I then took it out of 4X4 and the vibration went away. I drove it on the highway at 60 MPH no vibration. The next day I drove the car and the vibrations was back. Any suggestions would be greatly appreciated.

Wildfire67

 

I would take a very close look at the rear drive shaft.[hr]Make shure it is not bent and closely look at the u-joints.[hr]Pry them side to side and up and down with a large screwdriver to check for play.