Differential and Transfer Case Lubrication Selection

Just like engine oil, differential and transfer case fluid must be replaced at regular intervals. Not as often, but at regular intervals nonetheless. For maximum protection and to ensure optimal service life of these components, Chrysler Group LLC recommends specific fluids and drain intervals in the vehicle’s Owner’s Manual. These drain intervals may vary depending on the conditions the vehicle is operating under. For some vehicles operating under normal operating conditions there is not a drain interval; however, if a lubricant is contaminated with water, such as an axle that was submerged in water when launching a trailered boat, the lubricant should be replaced immediately.

Before replacing lubricants, you should be familiar with gear and axle oil classifications as determined by the American Petroleum Institute (API), which gives a service classification, and the Society of Automotive Engineers (SAE), which provides a viscosity number or numbers.

API SERVICE CLASSIFICATIONS

The API assigns service classifications according to the condition under which the lubricant should be used. API GL-4 and GL-5 remain the common classifications for automotive use. API GL-2, GL-3 and GL-6 lubricants are obsolete.

API defines API GL-4 as “…lubricants intended for axles with spiral bevel gears operating under moderate to severe conditions of speed and load or axles with hypoid gears operating under moderate speeds and loads.”

The API GL-5 classification denotes lubricants intended for gears, particularly hypoid, operating under conditions of high-speed, shock load; high-speed, low-torque and low-speed high-torque conditions. They provide greater load-carrying ability than API GL-4 lubricants. Never use API GL-5 lubricants where API GL-4 is specified.

SAE VISCOSITY GRADES

Viscosity indicates a lubricants ability to flow. The SAE has a numbering system to grade gear and axle lubricants. The lower the number the more easily it flows. Single grade lubricants have a single number, such as SAE 90. Multi-viscosity lubricants have dual numbers, such as SAE 80W-90 or 75W-140. A “W” (Winter) suffix means the lubricant has been tested at low temperatures. Lubricants tested at high temperatures do not have a letter after the number. Mult-viscosity lubricants meet SAE viscosity requirements at both high and low temperatures.

SYNTHETICS

Many automotive manufacturers recommend synthetic lubricants for certain components or certain driving conditions (i.e. trailer towing). These lubricants have several advantages over conventional oil, particularly under “extreme” conditions. For example, some benefits include their ability to transfer heat away from crucial differential parts quicker at extreme high temperatures and their ability to flow better at extreme low temperatures.

LIMITED-SLIP DIFFERENTIALS

Most limited-slip applications require a few ounces of friction-modifier additive. Chrysler Group LLC vehicles equipped with a Sure-grip, Power-lok, Hydra-lok® or Trac-lok® (clutch type) limited-slip differential require Mopar Limited Slip Additive, part no. 04318060AB. When replacing the differential lubricant, it is important to add this additive to the gear lubricant for the differential clutches. Failure to use this additive will result in clutch chatter and shortened clutch life.

TRANSFER CASES REQUIRING ATF

Unlike gear oils, ATFs do not carry a viscosity number, as the viscosity is part of the specification followed in formulating the fluid. Many older Jeep® and Dodge transfer cases require automatic transmission fluid. Mopar® ATF+4® Automatic Transmission Fluid is a fully synthetic fluid that replaces ATF+®, ATF+2®, ATF+3®, DEXRON®-II and DEXRON®-III fluids. In other words, use Mopar ATF+4 where the aforementioned discontinued fluids were recommended in Chrysler products.

SPECIAL LUBRICANTS

Some lubrication services require special lubricants that are not classified under API, SAE viscosity grade systems or are not common automatic transmission fluids. For example, the transfer case in the all-wheel-drive Chrysler 300, Dodge Charger and Dodge Magnum requires Mopar Transfer Case Lubricant – LX, part no. 05170055AA. Before refilling any differential or transfer case, make sure you are using the proper lubricant. Always refer to the vehicle’s Owner’s Manual for the lubricant part number.

Link - Complete list of Mopar Differential and Transfer Case fluids