Thunk from rear passenger over rocks and potholes.

Lifted rear under diff and got both wheels off the ground,put truck in neutral and spun both sides.
Doesn’t sound like the bearings are going out,put my hands under rear wheel wells on each side and lifted up and down a few times to feel for play between frame and bed,that all seems to be tight too.
Anything else I can try?

 

Check your leaf spring bushings or the packs themselves for a problem. Also check your exhaust to see if something is loose.

 

Had my rear shock do that. Brand new OME shock. Driving slow over bumps there would be a thump. Switched the shocks around and the thump went to the other side. Replaced the shock and the thumping was gone.

 

Could just be a truck thing or you’re hitting your bump stops. Check your leaf spring pack as StrangeDuck suggested, with the truck on the ground. From my understanding, these OEM leaf springs are not that great, as they’ll start to flatline or inverse bow. I think there are two sets of pack from factory, 3 vs 4 leafs. Even with the 4 pack, I’m somewhat flatlining with a camper shell on and I do sometimes hit my bump stops, hearing the thumps from the back, if I drive over bumps too fast.