Yeah I know they have to be broken in. Everybody's procedure is different though. This is what they recommend
After driving the first 15-20 miles at around 60 mph, it is best to stop and let the differential cool completely – usually about 1hr. You will do this 5 times for the first 100 miles of the breakin procedure. Maintaining a speed below 65 mph and driving conservatively for the first 500 miles is also advised. The gear oil should be changed after 500 miles. We recommend that you drive at least 500 miles before any heavy use or towing. During the first 45 miles of actual towing, only drive 10-15 miles at a time before stopping to let the differential cool.