Originally Posted by RedBullFiXX

Pulse
Your 12th scale has no slippers

Check diff tension with wheels mounted
Hold left wheel in left hand, right wheel in right hand
Use your thumb and index finger to turn the spur gear
The spur gear should be very difficult to turn, if at all

Always use a proper diff lube

Your diff should never slip on a 12th scale car, assuming you are on a decent race track, and not just playing in the street or the like

How to build a diff