Having a problem while slowing down still in gear, drivetrain noise

[SC61 MK3]

Getting a pretty loud noise from what sounds like the rear of the car when decelerating while still in gear, most noticeable at 40 or 50 mph. If I get up to like 50 mph while accelerating there is no noise but right when I let off the gas (still in gear, slowing down) it gets really loud but goes away if I give it gas and start accelerating again or push in the clutch.

Any ideas where to start?

 

[PureDrifter]

it goes away if you push in the clutch, but are still rolling along? then you can likely eliminate the rear end, rear wheel bearings, and possibly the driveshaft joints/bearing.

look at the clutch and trans perhaps?

 

[SC61 MK3]

Ya it goes away if I push in the clutch or take it out of gear and also if its in gear but I'm giving it gas and accelerating. Only happens when decelerating in gear

I was thinking clutch/tranny but wanted to rule out anything else before pulling the tranny... ugh

 

[IJ.]

Sight along the driveshaft and see if all the Uni's are in line o--o--o

 

[SC61 MK3]

Sight along the driveshaft and see if all the Uni's are in line o--o--o

Yes they are all lined up correctly per tsrm and all nuts/bolts are tight along the drive shaft, anything else to look for?

I also noticed with the rear wheels jacked up while in gear/ebrake up, the wheel has some play from side to side. Is that a problem with the rear diff? When i changed the diff fluid it had what looked like metal flakes in it