When I pull even a light trailer loaded with riding mower with my 2017 STX 4x4 5.0L crew cab, the truck feels like I'm driving with four flat-spotted tires, the ride is so bad. What gives? The truck is stock with no mods and the trailer is new. Tires are no issue. Truck rides quite smoothly otherwise. This happens even with different trailer attached, too.

 

Got enough weight on the tongue?

 

Light trailer and just a riding mower, so probably not much weight on the tongue. Light weight would create the truck bounce?

 

Have you replaced the stock rear shocks? It's pretty much a must on the aluminum trucks. You say the truck is bouncing, that is a symptom of the awful stock shocks. Replace them with bilstein's or FOX 2.0's and I guarantee your ride will be 100% better.

 

I wonder if the hitch is sooooo unlevel that it's binding over bumps.

 

Is the rider pulled al the way to the front? If not then do that.

 

Put a few hundred pounds in the bed of the truck, like sandbags. If that solves your problem, then you don't have enough tongue weight....

I don't know the solution, but maybe my suggestion will help you isolate the problem.

 

A high load over the trailer axle will do that. Normal bumps cause radical shifts in tongue weight. With my RS9000s I just crank up the damping a few clicks in the FRONT AND BACK. Sure hope I can find adjustable shocks when I get my new truck. Move the mower fwd of the axle should help.

 

I use a drop-down hitch which keeps trailers pretty level.

 

Will try your suggestion. Thanks!