DRAIN AND REFILL

The same procedure is used for both 4-speed and 5-speed transmission, but note that 5-speed transmission have two filler plugs and two drain plugs. Thus, to drain the 5-speed, both drain plugs must be removed, and to fill it, both filler plugs must be removed. The truck should be parked on a level surface, and the transmission should be at normal operating temperature (oil hot).

1. With the truck parked on a level surface (parking brake applied), place a pan of at least four quarts capacity under the transmission drain plug(s).
2. Remove the filler plug(s) to provide a vent; this will speed the draining process.
3. Remove the drain plug(s) and allow the old oil to drain into the pan.
4. Clean the drain plug(s) thoroughly and replace. Tighten to 15–20 ft. lbs. if you have a torque wrench handy; otherwise, just snug the plug or plugs in. Overtightening will strip the aluminum threads in the case.
5. Add lubricant through the filler plug(s) until it comes right up to the edge of the filler hole. Use SAE 90 EP gear oil. It usually comes in a squeeze bottle with a nozzle attached to the cap, but you can use a squeeze bulb or suction gun for additions.
6. Install the filler plug(s). Tightening torque is 15–20 ft. lbs. Check for leaks after the truck has been driven for a few miles.