Strange knocking/rattling noise in rear

[jace71]

When I let off the gas I hear a loud knocking noise coming from the rear of the 1009. Its not just one clunk, but a series of them until my speed drops. Sounds like someone is beating a the side of a garbage can with a hammer! I did notice that my right rear tire has no wheel weight, so maybe its causing enough vibration to rattle something?? What could cause a loud noise in the rear end when you let off gas? It seems to happen only at certain speeds too, around 45 mph

 

[Hogback Fabrication]

Check your u-joints.

 

[jace71]

Check your u-joints.

Will do...a bad u joint will make that much noise? I'm guessing to check the rear u joints I would set the parking brake, put the truck in neutral and check for play in the ujoints?

 

[Hogback Fabrication]

Will do...a bad u joint will make that much noise? I'm guessing to check the rear u joints I would set the parking brake, put the truck in neutral and check for play in the ujoints?

Yep and yep.