revo diff problems

i was rebuilding my revo's diffs today and im doing the rear one right now and after i put the new diff oil in and put it back together it seems really hard to turn. like once i had it all back together (in the bulkhead with the arms and axials on) it seemed really hard to turn with the axials. i even tryed the front one witch i have not done yet and it was really easy to turn.

i took it apart and it all seems right. even looked at it with the exploded version on the traxxas site and all the orings and washers are where they are needed to be.

any ideas.