I had this happen all the time when I ran my bias ply super swampers. It would only happen if I parked over night in the lawn or a gravel driveway. If I parked on cement or blacktop it wasn't anywhere near as noticeable. I would just be driving down the road and it would get a rhythm going and start shaking terribly. I too even pulled over once because it was so bad. It would go away if I just kept driving and heated the tires up.

 

ya i would get flat spots on my bias plys and the truck would shake a lil bit til the tires warmed up then it would be a smooth ride. then one nite i was driving home as i was slowing down to pull into a fuel station it wobbled very bad i looked and didnt see anything out of place i didnt do it again till 2 weeks later wen my brother inlaw was with me he was scared shitless and about to jump out of the truck once again it didnt do it till a week after that and now its worse everytime i drive it so far i had it realigned and cambers adjusted tires balanced and rotated!!!! i will check the hubs today and make sure nothing broke. wen i watch the tire wobble it looks like the axle is bent very bad or the rim once i slow down it rolls nice and straight and smooth! thanks for the inputs i greatly appreciate it!!!

 

That different tire and rim you put on, was it still bias ply? Try putting on a set of radial tires, I'd almost be willing to bet it goes away.

 

well hubs check out fine!! yes mdub i put another bias ply on it i was told to check the u bolts on the axle i found they where a lil loose but not to bad i still got between 3/4 - 1 full turn out of most of them one was real bad i got two and ahalf turns from it but it didnt cure it. i will try a set of radials next to see if it cures it!

 

It was the same problem I had man. It never really did it consistently, sometimes it was real bad, other times it wasn't too bad at all, sometimes it never happened. The only common denominator was where I parked That gravel driveway always made it happen, again, sometimes worse than others though. Really weird.

 

ya it does it all the time now as soon as i hit 35-40mph it shakes and wobbles like a dog shittin razor blades man its horrible, it is so bad now it broke my dash i park in gravel all the time it usually shakes a lil bit then once the tires warm up its fine but now its just rediculous. i have my inspection mechanic coming to look at it and drive it this weekend he has alot of experiance with lifted trucks and weak points in them so hopefuly we can get to the bottom of this and get it figured out.

 

Fisrt check your track arm bushings. The rod that is attached to the axel to the frame. Then check tires if you look at them and see cords or very bad uneven ware. Jack up the front and see how easy the wheels turn and look at the roter after removing the front wheels it should have even ware on both sides. Look at the brake lines if they are crackes badly that will be a problem also. Track arm bushing very easy and cheep to fix.
The next question is your truck jacked up or stock in hight and what kit is under it if raised? check for loose bolt and metal that the paint is flaked off sign of a bent items.
I wish you luck in finding the problem.

 

it has a 4inch skyjacker lift in it no track arms on it just the twin I beam with leafs in it.

 

went through it again found that the pitman arm nut was a lil loose i tightened it. i also noticed it looks like the driver side frame flexes a lil bit i looked for cracks in the frame and couldnt see any, i even wiped the frame down to get a better look. next i am gonna replace the steering box . also i noticed when i am in the truck turning the wheel i can hear somthing like its snapping or clunking but wen i look under with sombody turning the wheel i cant see anything out of place

 

Hey I was just reading through the post, I don't know if I have the same problem, but I get a little shake (not too bad) 'round the speed you are talking about.. I'm going to balance my tires, I only have a set of all season radials as I just got the truck. I guess I should check U-bolts, that hub 'n maybe the rims for any bends..

Another idea which I'm going to check is maybe the torque converter, as well as you should, maybe it feels like its from the passenger side but its the converter? Check this link I and see if the description fits. Do you notice it at all times or more so when you let off the throttle? could be torque tube bearings or something too.

torque converter shutter? - Ford Truck Enthusiasts Forums