At the specified intervals, the transmission fluid should be drained and replaced. Since the fluid will remain hot long after driving, perform this procedure only after the engine has cooled down completely. Before beginning work, purchase the transmission fluid specified in Recommended lubricants and fluids, a new filter and gasket. Never reuse the old filter or gasket! Other tools necessary for this job include jackstands to support the vehicle in a raised position, a drain pan capable of holding at least eight quarts, newspapers and clean rags. Raise the vehicle and support it securely on jackstands. Remove the transmission fill plug to allow for quicker draining of fluid. On later Expedition/Navigator models, the hot exhaust pipe is close to the fill plug area. Wear gloves during this procedure. With the drain pan in place, remove the front and side transmission pan mounting bolts. If your vehicle is equipped with a E40D transmission, ii may be necessary to disconnect the digital range sensor connector. Loosen the rear pan bolts approximately four turns. Carefully pry the transmission pan loose with a screwdriver, allowing the fluid to drain. Don't damage the pan or transmission gasket surfaces or leaks could develop. Remove the remaining bolts, pan and gasket. Carefully clean the gasket surface of the transmission to remove all traces of the old gasket and sealant. Drain the fluid-from the transmission pan, clean it with solvent and dry it thoroughly. Upon initial service most transmissions will have plastic plug lying in the bottom of the pan. This plug was used to keep contamination out of the transmission while on the assembly line. Discard the factory installed dust plug. Remove the old filter from transmission. If the filter seal did not come out with the filter, remove it from the transmission being careful not to gouge the seal bore in anyway. Install a new seal and filter. Make sure the gasket surface on the transmission pan is clean, then install a new gasket. Put the pan in place against the transmission and install the bolts. Working around the pan, tighten each bolt a little at a time. Don't overtighten the bolts! Lower the vehicle and add four quarts of automatic transmission fluid through the filler tube. With the transmission in Park and the parking brake set, run the engine at a fast idle, but don't race it. Move the gear selector through each range and back to Park. Check the fluid level. Add fluid if needed to reach the correct level. Check under the vehicle for leaks during the first few trips.
