Another drivetrain clunk

[maddawg89]

Hey, when I give the truck a bit of gas, just kinda goose it, there's a thunk, kinda like loads of slack coming out of the drivetrain and the rear diff. When I let off, it thinks again. I'm guessing that something is worn just not sure what. i can jack the rear axle up and put the truck in neutral and spin the driveshaft and there is a bit of slack there.... Any ideas? I want to get all these issues worked out so I can sell it.....

[jesilvas]

Slip joint most likely

I made my Samsung SGH-I997 send this.