Sonnax Zip Kit that reseals the worn main line, EPC, solenoid feed and converter circuits in Ford 4R44E, 4R55E, 5R44E and 5R55E valve bodies.
If you are rebuilding a 4R44E, 4R55E, 5R44E or 5R55E out of a Ranger, Explorer or Mazda B-Series pickup and the complaint was soft or erratic shifts, no third or fourth when hot, a second-gear start, delayed forward or a lockup that will not hold, the valve body bores are the likely leak. The Sonnax Zip Kit, part number 4R44E-5R55E-ZIP, is the one-box repair Sonnax built for this whole Ford family. It seals the worn main line, EPC, solenoid feed and converter circuits with drop-in parts, so you can rebuild the casting you already have instead of buying a complete replacement valve body.
These four transmissions share one basic valve body design, which is why a single kit covers both the four-speeds and the five-speeds. The PCM controls line pressure through the EPC solenoid, and that signal is multiplied by the boost valve before it reaches the pressure regulator. Separate forward and reverse modulator valves soften each engagement, and the converter regulator and TCC valves feed and apply the lockup clutch. Every one of those valves rides in an aluminum bore with no sleeve, and after enough cycling the clearance opens up and pressure bleeds to exhaust. The computer sees the result as a ratio or slip problem and keeps adapting until it runs out of range.
According to the Sonnax product page, the kit goes after those losses directly and also seals several circuits known for end plug leakage or poor checkball sealing. It adds separator plate modifications that firm up shifts, raise intermediate servo and direct clutch pressure, and improve TCC apply.
Bore wear and the 5R55 family's servo bore wear can look alike from the driver's seat. Start with a line pressure test and a scan of adaptive values, then work through our 5R55 harsh or delayed shifts diagnostic guide to rule out a servo or band problem. Once the valve body is on the bench, a vacuum test at each bore shows exactly which valves are leaking. Sonnax publishes a vacuum test guide for this family that marks the test points and the matching symptoms.
The kit is listed for the Ford 4R44E, 4R55E, 5R44E and 5R55E. Those units were used in the Ranger, the Mazda B-Series, and the Explorer and Explorer Sport. It is not for the later 5R55N, 5R55S or 5R55W, which use a different valve body and solenoid pack. Read the transmission ID tag before you order, and if you are not sure which unit you have, send us the year and VIN. You can browse every part we carry for this family on the 5R55 transmission parts page.
If the casting is cracked or the bores are beyond what the kit covers, a complete remanufactured 5R55E valve body is the better buy.
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Doing this repair right usually means replacing these at the same time. Same transmission, ships together.
No. The kit is for the 4R44E, 4R55E, 5R44E and 5R55E valve body. The 2002-and-later 5R55W, 5R55S and 5R55N use a different valve body and solenoid pack, so check your transmission tag first.
No reaming or reamer fixtures are needed. Several steps do call for drilling separator plate orifices to a set size, and the drill bits, a plug and rivets come in the kit. Basic valve body tools and a way to vacuum test the bores will help.
Often, yes. Sonnax lists TCC apply concerns and P0741 among the complaints tied to worn converter and modulator circuits, and the kit includes TCC modifications. But a worn converter or a bad TCC solenoid can set the same code, so test before you assume.
Use Mercon V ATF. Fill to the level on the dipstick or check plug with the engine running and the fluid at operating temperature, then reset the adaptive tables.
The kit includes new O-rings for the shift solenoids, but not the solenoids themselves. If a solenoid tests out of spec or the unit has very high mileage, replacing the EPC and shift solenoids during the same teardown is cheap insurance.
