5R55W Overhaul Kit 2002-2010, new and ready to install. Fits the 5R55W. Ships fast from the USA.
This is the reseal kit for a 2002-2010 5R55W or 5R55S, the five-speed behind the V6 and V8 in the Ford Explorer and Mercury Mountaineer, and the S version in later Lincoln LS, Thunderbird and Mustang V6 models. Buyers usually find it in one of two situations: the transmission is leaking from the pan, front pump or tailshaft, or it is already out of the truck for a clutch, band or pump repair and every seal that gets disturbed needs to be new. It is a Precision overhaul kit, reference KP53900S, covering the gaskets, oil seals, piston and lip seals, and the sealing rings that feed the rotating drums. Frictions, steels and bands are not part of it.
Transmission Digest describes the S/W as a heavily electronic unit: four on/off shift solenoids, a PWM converter clutch solenoid and three variable force solenoids that set the pressure on individual clutches and servos. Those solenoids can only do their job if the oil they regulate stays in its circuit. The seals in this kit are what hold it there. Piston seals let each clutch and servo apply with full force, the sealing rings carry pressure into drums that are spinning, and the pan, pump and case gaskets keep the whole system closed. As the rubber hardens with heat and age, apply pressure bleeds off, the computer adds more pressure to compensate, and the shifts get slower and softer until a gear ratio code sets.
Seals solve leaks and leaking apply circuits, but this unit has two known wear points that new rubber will not fix. Sonnax documents that the servo pin bores in the case wear oval, leaking overdrive and intermediate apply oil and burning bands, and that the VFS modulator bores in the valve body wear until the solenoids cannot get enough pressure to the clutches. Before you commit, read our 5R55W/5R55S servo pin bore wear guide and follow the pressure checks in the 5R55 harsh or delayed shifts walkthrough. Clean fluid with nothing on the magnet means seals and gaskets may be the whole job. Burnt lining in the pan means the clutches and bands need replacing too.
KP53900S is listed for both the 5R55W and the 5R55S from 2002 to 2010. Sonnax places the W in 2002-2003 Explorers and Mountaineers, with the S taking over in later trucks and replacing the 5R55N in the Lincoln LS and Thunderbird from 2003. It does not fit the older 5R55N or the 5R55E used in Rangers and 1997-2001 Explorers, which have different cases and valve bodies; our 5R55S vs 5R55W comparison explains the split. Check the transmission code on the door-jamb label, compare the pan gasket outline and pump seal with your unit, or send us the year and VIN and we will confirm before it ships. All of our parts for this family are on the 5R55 transmission parts page.
| Fits | 5R55W 2002-2010 |
| Part type | Overhaul Kit |
| Condition | New |
| Brand | OEM |
| Reference | KP53900S |
| Ships | From the USA |
| Warranty | 1-year |
Doing this repair right usually means replacing these at the same time. Same transmission, ships together.
No. KP53900S is an overhaul kit: gaskets, seals and sealing rings. If your fluid is burnt or the unit slips, add a friction and steel kit and new bands, or choose a full rebuild kit instead.
Yes, the kit is listed for both from 2002 to 2010. It does not fit the 5R55N or the 5R55E, which are different transmissions. Confirm the code on the door-jamb label before ordering.
A front leak is often the pump seal, and this kit includes the gaskets and seals for a full reseal. The transmission has to come out to replace the pump seal, so most owners reseal the whole unit at that point instead of doing only the front.
Mercon V. There is no dipstick; the level is set at the check plug with the engine running at operating temperature. A remanufacturer guide lists roughly 11.2 quarts dry for the 3.0L and 3.9L and 12.4 to 12.7 quarts for the 4.0L and 4.6L.
Only if the cause is leaking seals. Sonnax documents worn servo pin bores and worn valve body bores as common causes of band slip and gear ratio codes in this unit, and new seals will not fix either. Check the bores before relying on a reseal.
