5R55W Overhaul Gasket and Seal Kit, Explorer 2002-2010

This is the soft-parts half of a 5R55W or 5R55S overhaul: the cork pan gasket, pump and case gaskets, piston and drum lip seals, the front pump seal and rear extension seal, and the small O-ring assortment for the solenoid pack and case connector. It crosses to the common kit numbers KP53900SX, K56900KX, T16002G and T16002GA. Frictions, steels and the filter are not included, so this is the kit for a unit that is coming apart for leaks or a reseal while the clutch packs still measure in spec.

Fitment is Ford's five-speed rear-drive family: Explorer 2002-2010 (4.0L V6 and 4.6L V8), Explorer Sport Trac 2007-2010, Mercury Mountaineer 2002-2010, Mustang 2005-2010 (4.0L and 4.6L), Lincoln Aviator 2003-2006, Lincoln LS 2003-2006 and Thunderbird 2003-2005 with the 5R55S. The W and S share the case and nearly all of the soft parts.

The problems this kit fixes are the slow ones. A hardened front pump seal or pump body O-ring is the usual drip at the bellhousing. Tired servo cover O-rings bleed off apply pressure, which shows up as a flare on the 2-3 or into overdrive and a lazy engagement after the truck sits overnight. Brittle drum and piston seals let a clutch pack slip under load long before the frictions are actually burned.

On the bench, replace every lip seal and O-ring as the drums come apart rather than picking the ones that look bad, lube new seals with assembly gel or clean ATF before installing the pistons, and air-check each circuit before the unit goes back together. Torque the pan in a criss-cross pattern and refill with Mercon V.