When building the rear diff on the ec, i can never get it really smooth. is there any tips to getting it better?
First thing is to get the U1954 thrust bearing; this will last you all season
(remember 1 washer is slightly larger).
Then use the female outdrive to sand both sides of the diff-rings on a hard, smooth surface. Clean everything very good and then apply rings to the outdrive with the squared edge of the ring towards the outdrive (grease the outdrive per manual). Apply a thin layer of grease on the whole ring and then build diff per the manual.
Make sure you use Schumacher diff grease and break-in the diff before running!