Chevrolet Repair: 95 chevy Pickup 4 wheel drive vibration, pitman arms, cv joints

Question
Front end vibrates on the PU - left side mirror shakes tremendously (60 to 70 mph) while the right is rock steady.  I have replaced all ball joints, tie rods, pitman arms, replaced tires, new wheels, new u-joints, & pinon bearings.  I recently noticed that the vibration disappears while in 4 wheel drive, reoccurs in 2 wheel drive or if I let up on the accelerator while in 4 wheel drive.  I'm now suspecting left CV joints (1/2 shaft) even though the boots look excellent.  Any other thoughts?

thanks
rickey

Answer
Hello Ricky,
Sounds like you are in the right area, but if you don't find a problem with that half shaft, grab the flange that it bolts to on the front diff housing, and see if there is any slack up or down in it. I am thinking differential side gears.
You said you replaced pinion bearings....front?? If so, may I ask why?

The part about disappearing in 4X4 while under acceleration, but reappearing during decel and non driving, makes me think the front pinion is torquing the side gear into the bearing, and centering it while under strain, and allowing it to loosen and wobble while unloaded.

Van