Had my new diff fitted Saturday from 3.92 to 3.62. Diff was a nice gift from steve (Coozer) Well it certainly feels a bit better and seems like its not getting to red line as quick but its makng a slight knocking sound from under gear stick

Any ideas ?

Loose prop??

I was thinking that checked front and back best i could but seemed ok seems to be middle area so will have to take underneath off

sound can travel.

check the bolts on the drive shafts.

Dropped it into garage that changed the diff for me and he took it for a blast said he carnt feel any viration or slight knocking but when I took it in my son and me could here and feel it I could even feel and see vibration through the steering wheel especially after doing 90 + then letting slow down around 60 and 70mph

Any more ideas ?