lightning epx diff upgrades

Hey guys. 
I got a front one way and 1.4 times rear gear for the lightning epx and only when i have the diff's together it seems like the gear mesh is to tight. if it turn it by hand i can feel the gears meshing. so would i be right in thinking that the bearings are a causing this and just shaving a little plastic from the diff where the bearings sit will help with this or do you think it's something else?