i have swapped tires and shocks on the back, nothing changed. do you think it would be the front that is shaking?

 

Are saying its shaking that bad when you are driving on flat surface or over bumps?

 

flat surface, everytime i get around 53-58mph it will bounce.

 

Most likely not. There can be a couple of other things causing the bed to shake:

1. Out of round rear rotors.
2. A bent or out of balance rear rim.
3. A non-concentric wheel hub (wheel doesn't mount level onto the rotor)
4. Bent rear axle (left or right)

All of this can cause shake. What can also cause shake are oversized wheels. Anything larger than stock or larger than stock rims (21"+) can cause shake. Balancing can be a challenge. Road force balancing can really help.

 

i have swapped wheels and it did not change. truck is an 06 v6 with 55k miles , brakes looked good when i was swapping wheels, didnt really spin them to see if they were ob longed....but it just does it at like 55mph, no other time. it has 265/70r17's tires.

 

When I bought my '01 Super Duty, the bed shook until I put a toolbox on it. My '04 F150, the bed shook until I put a toolbox on it. On my '06 F150, the bed shook until I put a toolbox on it. So, put a toolbox on it and it won't shake too bad.

 

There is actually a difference in the years. I know the '07s have a support right behind the rear tires that wasn't there on the earlier years. I had a '05 Screw that didn't have the bed supports, but my '07 has them. The bounce is almost barely noticeable compared to my '05.

 

How many bolts are holding down your bed?

 

Have a mechanic check the runout on the hubs. That will indicate a problem with an axel.

Are you the original owner? Have you hit any curbs at high speed? Has the bed been overloaded?

 

i have 6 bolts.

and i have not hit any curbs or overloaded the bed