I can't source the cause of this horrible vibration.
I have replaced the motor mounts, universal joints and front wheel bearings.

92 dak sport ext. cab 3.9L v6.

The vibration comes and goes. It is not a rattle.

Anyone know how i can source the cause? Possibly support bearing for the drive shaft?

 

Bent wheel?

 

Tire out of round?

 

Easy to check.

 

guess the only way to test that is to take it into a shop eh?

 

oh, this problem only happens when I am giving it gas. once I coast and let off the gas, it stops vibrating

 

Sounds like a bad u-joint.

What is the frequency of the vibration? Is it wheel speed, engine speed, or driveline speed? It can be hard to feel the difference between engine speed and driveline speed, but you can tell by driving at the speed where the vibration occurs, then shifting out of overdrive while maintaining road speed. If it changes, it's engine-related. If not, it's driveline-related.

 

Funny you mention u joint.
I did the single u joint a month ago (mine has 3)
Then two weeks ago I did the motor mounts.
Seems logical that the stronger more stable drive train has pushed the last two over the edge.
I think I will do the other two.

 

If the U-joints don't work, you may want to try getting the drive shaft balanced.
I had to do that on an S-10 with a 3 piece shaft.

 

Is your driveshaft a 2-piece? If so, did you separate it? Did you put it back together the same way it came apart? Did you put the c-clips on the new u-joint to center it in the yoke?