I hear it when I'm backing into a parking space or backing into my garage. I first thought it was the metal guard around the disc brakes catching, but I jacked up the truck and spun the wheels around and couldn't replicate the noise. And it clearly only happens when I shift to reverse and start moving. And I can tell it is making revolutions, a repeating sound that can go slower or faster.

 

guess!, loose pads.touch brake lightly going back, see if?

 

Cat heat shield, they get old, corroded and rattle under low speed load. Get under there when it's cool, and bend it away from any contact.

If you doubt it, lay on the ground next to the truck (Keep away from tires!!) while someone slowly backs up a slopped driveway, you can then pinpoint the source.

 

mine was the heat shield for the oil pan or transmission pan....was rubbing the driveshaft

 

That has happened with the gas tax skid too.

Manson check your drive shaft for radial scraps (shiny ).

 

I'll try those, thanks for the replies!

also, it only happens when I engage the clutch in reverse, weird