ARB RD81 - Manual (Page 20)

4 Installing the Air Locker
18
Install the bearing caps oriented as they were marked before they
were removed, and tighten the bearing cap bolts. It is not
necessary to torque them down at this time.
Check that some backlash can be felt between the ring and pinion
gears. No backlash would be an early indication of incorrect shim
thickness.
4.5 Checking the Backlash
Relieve all tension on the housing spreader.
Tighten all bearing cap bolts with a torque wrench to the torque
specified in your vehicle manufacturer’s service manual.
Set a depth indicator on one of the ring gear teeth as in
Figure 11.
While supporting the pinion gear by holding the drive shaft, rotate
the differential in both directions while observing the maximum
variation in depth from the indicator (i.e., the highest value minus
the lowest value). This value is referred to as the ring and pinion
backlash.
Rotate the differential center 90
° and measure again for accuracy.
Figure 11.
Refer to your vehicle service manual for the specified maximum
and minimum amounts of backlash. If the backlash is not within the
specifications then the differential will have to be removed and re-
shimmed.