How to Change the Ford 9 Differential Fluid

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Ford's 9-inch differential is known for its durability.

wrench image by AGphotographer from Fotolia.com

Along with the 10-bolt differential produced by General Motors, Ford's 9-inch differential is among the most popular differentials with automotive enthusiasts. Ford first produced the 9-inch differential in 1957, but eventually phased out production by the end of the 1980s. The differential consists of two gears, which rotate along with the drive shaft. The differential makes use of a heavy fluid, which keeps the gears lubricated and cool. The fluid can be quickly changed with the assistance of a fluid pump.

Difficulty: Moderately Easy

Instructions

1. Position a trolley jack underneath the center of the differential, then use the jack to lift the vehicle. Slide a single safety stand underneath each axle shaft, then lower the vehicle onto the stands.
   
   
2. Remove the oil filler plug from the front of the differential, using a wrench. The front of the differential is the side of the differential on which the drive shaft is bolted.
   
   
3. Remove the old differential fluid. The 9-inch differential does not feature a drain plug. The fluid must therefore be pumped out of the differential with a fluid plump. The fluid pump features two hoses. Insert the hose at the base of the pump into the differential. Insert the hose at the top of the pump into a container, then operate the pump to remove the differential fluid.
   
   
4. Insert the bottom hose of the fluid pump into the container containing the new differential fluid. If the vehicle will be used in cold climates, the differential should be filled with SAE 80 hypoid gear lubricant. For normal operation, use SAE 80 hypoid gear lubricant. Insert the hose at the top of the pump into the fill hole on the differential. Use the pump handle to fill the differential until the fluid level is just below the filler hole.
   
5. Insert the filler plug into the differential, then tighten the filler plug with a wrench.
   
   
6. Lift the vehicle with the jack placed underneath the differential, remove the safety stands and lower the vehicle to the ground.
   

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