The axle shaft tapers have "teeth" that cut into the smooth surface of a new rear wheel hub casting.  There is a minimum beginning axle shaft nut torque on Jeep CJs of 250 ft-lbs. For a new hub, this is followed by tightening the axle shaft nut further until you achieve the factory-specified stick-out length of the axle shaft threads (beyond the outer edge of the wheel hub).   Note: I've attached the factory procedure in a PDF for those interested in the Model 20 AMC Jeep CJ axle shaft hub ins