B4.1 gear diff rebuild

[haggis]

Just dismantled my b4.1 rtr gear diff

Put it all back together with the rebuild kit as per the instructions and it is horrific

Locks up and basically is not how it should be

Is there anything daft I might be missing.

The shims on the outdrive seem super tight cause the instructions says to use 2 shims. I've tried with 2, 1 and the old one and can't get this normally smooth diff rolling again