Drive the vehicle for several miles to warm up the differential oil, which will make it drain better.
Raise the vehicle and support all four wheels with jack stands. You can skip this step and still perform the task, but there will be limited room to maneuver beneath the truck.
Place the drain pan beneath the front differential drain plug, located in the bottom center of the differential.
Use a socket wrench to loosen the drain plug. Continue to remove it by hand until you can pull it free.
Allow the oil to completely drain, and replace the drain plug. Tighten with a torque wrench to 20 foot-pounds of torque.
Use a socket to remove the front differential fill plug, which is on the rear of the differential, directly above the drain plug.
Use a hand pump or large syringe to fill the differential with oil. Continue until the oil begins to overflow from the fill hole. Replace the fill plug and tighten it to 20 ft-lbs of torque.
