Shady9503

hey there, i had a problem with my earthquake 3.5 where for 5 mins it runs fine then all the power shifts to the front wheels, i waited a bit took it apart to see if maybe the grub screw was loose but it wasnt so i put it back together ran it again it was fine for another 5 mins then again all power to the front wheels so i got a new differential now when im trying to install it im putting in the screws to seal the differential but when i tighten them i spin the drive cups with my hands but they seem to lock up? when i loosen the screws a bit again it spins fine? just wondering how to install it properly! thanks guys