Noise from spur

[minke]

I decided to rebuild my diffs, just because there was the smallest amount of oil near the outdrives, turned out to be fine.
Anyhow when I had it all together the spur screams like a banshee, mainly when moving off.
I tried different pinions, no change.
Changed the spur, no change.
I have a complete spare slipper assembly, tried it and no change.
The rear slipper mount is still plastic and I haven't changed it, but did just about notice the most miniscule plastic dust/shavings under the bearing and under the motor on the chassis.

So is it a bearing problem? should I change the mount? or is it something else? I can't see any rubbing or binding or deformed parts anywhere.