Rear end popping or knocking noise in my wonderful car

[Judder]

Hi ,

i am the proud owner of a 6litre 2007 SS Crewman, unfortunately i am having trouble locating a very annoying popping or knocking noise in the rear end.
I have had Holden here in Hamilton new Zealand look at it and it seems, it is a sound no one can find............i am not sure why. we can all hear it and initially blamed on strut bushes, these have been replaced. The noise is still there please understand this Ute has only done 50,000kms

The Noise appears normally after initial acceleration and not necessarily as it changes stages, but most definitely as you release pressure off the accelerator, the noise is a deep sounding knock or pop, also happens during hill acceleration, when you button off the gas...............

QuestionS, could it be leaf spring movement, could it be a noisy non return valve (if there is one) from the gas tank............god i dont know i just want to know what it is so we can fix it.

I had a 2002 VX SS about 5 years ago that did this also but being a sedan this was not so noticeable

Please help its driving me nuts

Cheers

[Judder]

another thought on this if there are any suspension specialists out there, the ute is lowered but seems to be with the use of blocks, has original struts and leafs, so my question .............Could it be movement within the struts itsself, as it is not so apparent during normal travel it is just as the cars plains, if you know what i mean after initial excelleration and at about 2nd or third stage dependand on speed