ARB RD74 - Manual (Page 33)

6 Testing & Final Assembly
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The wheel should rotate freely and the opposite wheel should be
turning in the opposite direction without any resistance or
mechanical noise from within the differential.
Turn the Air Locker switch to the ‘ON’ position. The illuminated
symbol on the switch cover should light up.
Rotate the same wheel again.
Both wheels should rotate together.
Turn the switch off again.
Rotate the same wheel.
The wheels should again rotate in opposite directions.
6.3 Filling the Differential
NOTE : Consult the ARB Air Locker Operating & Service
Manual for recommendations on differential lubricant
specifications.
Refill the differential until level with the filler hole.
Rotate the differential center 2 full turns.
Check the oil level and add oil if necessary.
Apply thread sealant to filler plug before inserting.
Replace the filler plug.
Clean the differential housing of any oil or grease that may collect
dirt or other abrasive particles.