ARB RD139 - Manual (Page 12)

3 Installing the Air Locker
10
Figure 4.
3.2 Drilling and Tapping the Bulkhead Port
An air line port must be drilled and tapped through the differential
housing to mount the bulkhead fitting into.
!
Mark a spot on the top of the outside of the differential housing that
will be clear of the Air Locker once the seal housing tube has been
installed. (Fig.5.)
Figure 5.