Letting off the gas with the power still in the drivetrain ( clutch not pushed in ) I am getting a wop wop wop wop wop kinda noise coming from the rear end... my driveshaft is fresh with new hangers and all... so 99% sure its coming from the diff... possible shimming problem?? (Lalilberte's suggestion)... anyone know of any weak spots on the diff that I should be checking out?? The noise goes away when I push the clutch and take the power away from the drivetrain I should add!..... and only on deceleration, acceleration is perfect.

Did these new hangers include proper spacers? Did you change the carrier bearings while you were at it? Are all sections of your driveshaft at the correct angles?

yes carrier bearings were changed as well.. complete new rebuild of the shaft.. shaft seems to be angled correctly as well... i will double check the angles tomorrow in the day light though and get back to you...... "spacers" your just talking the spacers that are used with bolting it to the car?

Sounds very similar to my drivetrain clicking... when I was off the throttle my car made lots of clicking, on the trottle it's perfect. Mine turned out to be my transfercase. I too for a while thought it was the pumpkin, but t-case fixed it.

The noise is nothing like yours Eric. The noise is coming from the rear diff and it's more of a growling on Decel only.

This is a common issue for 1G's as the diff wears. Mine did the exact same thing. Check your fluid for large metal particles, if there are none you are probably ok. Also ensure your fluid is topped up. This is due to the rear diff wearing in over time.

A few part numbers you can look at:
MB241903 - SPACER SET RR DIFF
MB185340 - SPACER SET RR DIFF
MB185360 - SHIM SET, RR DIFF DRIVE PINION FR
MB185350 - SHIM SET, RR DIFF DRIVE PINION RR

If you find metal particles, good excuse for a 4 bolt swap.

After searching, a few things I have come up with are as follows:

Incorrect final drive ratio - This would not apply as you had the original tranny in your car in the first place
Driveshaft Carrier Bearings - All brand new, so it can't be that
Thrust bearing failure in the differential - Usually you will hear this during accel, decel and clutch in or out. This is only happening clutch engaged in decel.

Well whenever that damn clutch gets here and you come put my new goodies in with me we will check it out... but all fluid are fresh, there were no shavings at all... .. remember just had my rearend out??? it was "checked" but Im sure nothing was checked shimming wise or anything technical!..... but well drain it again of course.. lots of Amsoil lying around ....

Oh yeah, I forgot your rear diff was out. Find out if they checked the lash in your gears.

The mechanic was a dickhead.. and prolly didnt do anything... it was just there cuz we broke all the bolts on the cover and he machined them out... and he checked out the diff... but you heard it.. no need to explain to you on here.. well see this week when its together again.... but I will talk to u in the morning when I am there.. msg my phone when your up!

I realize this is a slight bit on the old side. But i thought i would share my experience with this noise.
I had a wop wop wop grinding whining type noise in my 1gb during clutch out decel. In the car, sounded like textbook rear pinion noise. So out came my 4 bolt, 300$ worth of bearings later, everything reassembled the noise was exactly the same.
Turned out that the noise was somehow carrying from my transfer case. The noise was in the output shaft bearing and carrying through the driveshaft to the floor i suppose.
Thought I would share in case anyone else gets in my predicament.