Trying to track down a thunking noise in my driveline. Basically if I am crusing and let off the gas to a coast, and then get back on the gas it makes a loud thunk and then is fine. Also when letting off gas it thunks as well. rebuilt driveshaft, new mounts everywhere. This video isnt mine but almost exaclty what is going on with my tcase.

 

Probably not much help here. Suspecting ring/pinion clearance in the differential. Find the play? Jacking up one wheel in park and watching the drive line might be a thought. If there isn't play in the diff pinion I'm lost for now.

 

There is play in the rear end, if you spin the wheel it has small movment before it catches. front driveshaft is currently disconnected.

 

I agree, probably worn rear end

 

greaaat. having a locker in the rear wouldnt affect your diagnosis would it?

 

It might, depending on what type of locker. But that could mimic a worn ring and pinion when shifting directions. Does it feel like the rear end shifts when this happens?

 

It's a Spartan autolocker. And what do you mean by shifts? The best way to describe it would be like if i step on the gas when its coasting, its like something slips and slams into a notch, and then is locked in and doesn't make anymore movement.

 

My old 79 Chevy had this exact problem(np203). It was a loosey goosey transfer case chain.

Not saying that is your issue but its something to check into if it turns out to not be the rear