Ok , when I hit about 60 getting on the highway until around 70-75 truck vibrates so bad it feels like a wheel or two is gonna fly off.Then it goes away. I can feel it in the steering wheel and the seat of my pants. I can also hit bumps all day at any speed and it doesn't do it, so I assume it not death wobble. I'm going to get the tires balanced Saturday(again) some place different just to see. But, I'm pretty much at a loss for what to try next. Other than trying another place to check out the caster and seeing if it's maxed, but I don't think it would do what it does between those speeds only. I guess the only thing I can think of is the damn goodyear wranglers have broke a belt since last rotation and balance. Any other thoughts?

Thanks John

 

how old are your tires?

 

Probably about 2 years old, regularly rotated and balanced. Also about 15k and more than half the tread left.

 

that really doesnt sound like a lumpy tire, you would notice it constantly above 50, and it wouldnt go away.

Maybe a froze up u-joint?

 

I've heard of unbalanced driveshafts causing vibration, but that usually only happens down at low speeds. and I can't imagine it would be that bad.

My dad once had a problem on his ford van when the tire mechanic didn't tighten down the lug nuts and the rim shook on the lugs.