ARB RD93 - Manual (Page 11)

2 Removing the Existing Differential
9
IMPORTANT:
Some Salisbury axles were manufactured with poor oil drainage
between the axle tubes and the differential housing. This can often
result in one of the axle tubes filling up with differential oil while
running. In most cases this will result in a blocked air vent which
will cause the differential housing to pressurize and expel oil from
the axle seals at the wheels or force oil into the air system of the Air
Locker, eventually expelling oil at the solenoid valve. This is a
design flaw which was corrected by most automakers in the later
releases of their axle assemblies. If no lower drainage point is
present in the differential housing then it is critical that you modify
the housing to include one.
Inspect the differential housing for the presence of adequate drainage
in both axle tubes (refer to Fig.4.).
Figure 4.
If drainage is inadequate or does not exist then a slot or hole should
be cut into the housing on the lower side of the tube(s) to allow oil out
of the axle tube area.
NOTE : Make sure any grinding dust, filings or drill chips left
behind by cutting the drainage slots is completely
cleaned out of the housing.
Check that the axle air vents are clear and working correctly.