I got a 2010 f150 supercab, rear end bounces going down the road. Starts at 30 and gets worse. Put in new shocks and u joints. Had springs looked at and they aren't worn, had driveshaft balanced and that didn't fix issue either. Tires are brand new and balanced. Had a Ford dealer look at it but they aren't sure of the issue either. Don't really want to start replacing things just to see if that fixes the issue because that can get expensive. Anyone else experience this issue?

 

If what I am suggesting might have been overlooked, worth checking.
Sometimes when tires get mounted on the rims , they don't always mount them evenly, the same distance between the line on the tire and the rim. This can be easily checked by lifting the rear wheels off the ground , placing a stationary object next to the bottom of the tire and rotating the wheel to see if the distance from the ground or object is equal all the way the tire is rotated. I have found some surprising results in doing those checks.

 

I checked the tires out and all seems to be good. Even rotated them and still bounces the same.