Thanks Robbie,
yes car is ballraced throughout and gearbox runs smooth without pinion attached (but this is not under loading) so will just have to accept the noisy gearbox I think. I will repack with grease as the grease will supress excessive noise. As for the motor screw, I suspected some work with a dremel might be required
.
On another note, the manual gave no guidance on diff settings, so I set it to allow for a small amount of slippage (as i have done for other car diffs) and the diff action felt very smooth before installing so hopefully that is not contributing to the noise.
Cheers
Si