NEED HELP... where's the noise coming from??

['70_402]

I have a growl/grind noise coming from what feels/sounds like the trans area of my truck when i let off the accelerator. This has been there since i swapped the LS and 4l80E into my truck... i have since completely rebuilt my transmission (new torque converter) and rear end. I have a new driveshaft that was built when i did the swap. Its only when i let off the gas.. i can roll on and off the throttle and it comes and goes. does it in gear and in neutral while coasting. I have trailing arm suspension so my pinion doesn't rotate while under/not under load....

The noise was there before and is still there through all the things i've changed out chasing this growl.

Any ideas???