Vx ss rear knocking shudder diff

[FLYIN350]

Today i did a diff oil change on my 02 VX SS using Castrol LSD oil. After having done so I took it for a drive and when i medium to hard accelerate there is a knocking pulsating shudder coming from the rear region of the car. If car is driven softly there is no noise but when under hardish acceleration it is there. I wento holden and they sold me some DIFF additive which i put in and that has not solved the problem. The car was put on a hoist while i did this and i read on some forum that the shafts can become dislodged when hanging on a hoist. I find this situation very strange as renewing diff oil should not cause more problems. The car has 115 000kms and has been well serviced. This car is my pride and joy so I hope you guys can give me some clues as to what it could be. Cheers

[fixitdude74]

general consensus is the vehicle needs to be driven for 100km, to allow the additive to 'do its thing'.
i have VX Calais series II 5.7 and it was the same, i changed the oil and added the genuine GMH LSD additive, took it for a drive
down to adelaide river and back, roughly 155km, and now its quiet az

PS: only use GMH recommended Diff oils, some aftermarket oils do not meet specification and can stop the additive from working.