i need help my rear of my car shudders at about 80kph when i hit the gas

[NVME-69]

I had a similar issue when I converted from auto to manual transmission. It turned out that the phasing of the tailshaft was wrong. The tailshaft was overhauled during the trans conversion but was not installed properly.

yer thats what i think it might be too i will talk to the tranny and diff bloke on tuesday

cheers bro