Originally Posted by sflash868
Ok, I'm going nuts with this. I have like 400 problems that all contradict each other. Basically the truck is all over the road handles like crap, vibrates like all hell at 50 mph, changes direction when on and off the gas etc.
Sounds very like rear axle steer to me. I had this once when the nuts on the trailing arms backed off. Coming off/on the power needed to be accompanied with about 1/2 turn on the steering wheel - undriveable.
A frame ball joint is much less noticeable - usually a knock when taking up drive - very slight change in direction.
I had a very bad result once when I changed out only 1 of the rear trailing arm to chassis bushes, they soften in use and the new one was harder = massive rear axle steer. Always change as a pair.
Are the prop shaft balancing weights still on, small rectangles of steel tack welded to the propshaft that could cause vibration if they've been knocked off. Also look at the bearings on the transfer box output shafts and diffs for play. There's always some play at the front output shaft though.
Hope this helps.