ARB RD142 - Manual (Page 13)

3 Installing the Air Locker
11
Figure 5.
3.3 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 housing (opposite the ring gear) in an
area well clear of the differential, the ring gear, and any other
obstructions that could snag the seal housing tube. (Fig.6.)
Figure 6.