dhall50

Symptoms:
Bad shimmy/vibration at 48-55
I can hear a whoom whoom sound
Bed shakes like crazy as does the tranny and t case shifters at those speeds
Whole truck is moving enough it makes my mirrors blurry

What has been done thus far:
Swapped both rear axles
Put in a spare rear drive shaft with brand new U joints
New tires (and balanced) (and rotated to see if different---Nope) Rims are a year old.
Tightened rear end flange nut that was a little loose.
These helped a little but after driving it it is still pretty bad.

We are guessing with how the bed and tranny etc moves that its in the rear. Can a bent rear axle housing cause a wobble? I picked a spare up for $20 today but I was thinking it would just cook tires and not cause a wobble. Since I know its not the axle shafts, drive shaft, wheels, tires. Where do I go from here. On jack stands you can feel it kind of but I cant really say where its coming from visually. Do you think its in the rear from what I described? Any input is appreciated.

Yes, I searched.

yotaman90

I feel that you are correct in thinking that it may be the rear third. My 87 has a similar vibration problem, but the input shaft on the third has some play in it and the seal leaks pretty badly. I figure that that's the problem, but I need to pick up a good used third to test my theory