I have a '89 4x4 pickup , 4x4, 22RE that has a vibration in the drive train.

At highway speed if you push in the clutch the rear vibrates (you feel it in the seat) or if you put it in neutral and coast it vibrates. If I push the gas pedal just slightly you can also feel it and it goes away when you push the pedal on down.

Under throttle it does not vibrate nor does it vibrate coming down a hill (off the throttle) Now is this the symptom of driveshaft problem or the 3rd member ?

 

sounds like bad u joints also could be the carrier bearing. if u have one. if u get under it and grab the drive shaft and try going back and forth u might be able to see where the movement is and what one is bad.

 

doesn't have the carrier bearing, and i put new ujoints in last month ?

 

its possible there is excessive play in your slip yoke. that happened on mine.

 

I had bad u joints and it vibrated when I was on the throttle , when I let off it went away . Usually if it vibrates when u lay off the gas it's something in the rear end .