ARB RD101 - Manual (Page 24)

3 Installing the Air Locker
22
Figure 16.
c Tap the factory shim into place between the seal housing and the
aluminum housing with the notch lined up with the notch in the seal
housing and the notch in the aluminum differential housing.
(Fig.17.)
Figure 17.
NOTE : Do not spread the housing on the aluminum models.
c Check that some clearance exists between the bearing cap and the
seal housing tube. If not, the bearing cap should be removed and
the tube re-bent for adequate clearance.
c Check that some backlash can be felt between the ring and pinion
gears. No backlash would be an early indication of incorrect shim
thickness.