DIFFERENTIAL LUBRICANT
The differentials transfer engine power to the drive wheels, enabling the vehicle
to move forward or reverse. Differentials are sealed units that have gears,
bearings, and axles that house their own lubricant. They must be inspected and
maintained. Fluid level, color, consistency, and smell are critical when inspecting
differentials. Differentials use one of three fluid types: motor oil, automatic
transmission fluid, or gear oil. Your owner’s manual will tell you exactly what
type of lubricant is used.
Color
Healthy differential fluid is red (automatic transmission fluid), caramel (motor
oil), or black (gear oil). Inspect closely for the presence of metal flakes because
they indicate internal wear. If metal flakes are present, open the unit and inspect
it thoroughly before putting it back into service. Left to operate with wear, the
differential will eventually fail. A milky color means moisture is in the system,
and the gear lube must be replaced immediately or heat and friction will buildup
and the differential will fail.
Consistency
Differential lubricants should be smooth and slippery to the touch. Grit indicates
the presence of dirt or wear material. Further inspection is warranted to prevent
premature component failure.
Smell
A burnt smell indicates internal overheating caused by friction and lack of
lubrication. Open the unit and inspect for ring and pinion, carrier, axle, or pinion
bearing wear or failure as well as leaks.