4R55E Pressure Control Solenoid, new and ready to install. Fits the 4R55E. Ships fast from the USA.
A 1995 or 1996 Ford Explorer, Ranger or Mazda B4000 with the 4.0L and the four-speed 4R55E that suddenly slams into Drive, flares between gears, or sets an electronic pressure control code is the truck this part is for. It is a single new EPC (electronic pressure control) solenoid listed under reference D56431A. In the Transtar catalog D56431A is the Bosch-built EPC solenoid with two red inlet screens on the nose, and it has since been superseded by Rostra A56431A, the same part number family shops use for the whole 4R44E, 4R55E, 5R44E and 5R55E line. It bolts to the valve body, so it is replaced through the pan opening without pulling the transmission.
The 4R55E has no throttle valve cable and no vacuum modulator. The PCM sets line pressure by varying current to this solenoid, and the solenoid's output oil works on the boost and main regulator circuit to raise or lower mainline. That mainline feeds every clutch and band in the transmission and also feeds the converter clutch regulator, so a weak EPC signal can show up as converter slip as well as soft shifts. Sonnax describes the line rise path on this family: as EPC output climbs, an engagement control valve opens to line pressure and boosts it further, which is what gives the 4R55E a firm garage shift into Drive and Reverse. The circuit fails safe toward high pressure, so a dead coil or open wire usually means harsh shifts, while a sticking or contaminated solenoid tends to cause the opposite.
Check the fluid level and condition first. Then pull codes and note whether they are electrical (open or short) or performance related. Unplug the case connector and look for ATF wicking into the pins, which can set intermittent EPC codes by itself. Ohm the EPC circuit at the connector; our multimeter solenoid test guide shows how. The real answer comes from a pressure gauge. Sonnax lists good maximum EPC pressure on this family at roughly 125-130 psi in overdrive and up to 144 psi in Reverse, with no more than about a 15 psi drop when the converter clutch applies. If line pressure tracks the scan tool command, the solenoid is working and the fault is hydraulic, usually worn boost valve or regulator bores. The steps are laid out in our line pressure checking guide.
The 4R55E was the 4.0L version of the 4R44E, used for only a short run before Ford turned the same case into the five-speed 5R55E for 1997. The A56431A interchange that replaces D56431A covers the 4R55E for 1995-1996, the 4R44E for 1995-2001, the 5R44E for 2001-2011 and the 5R55E for 1997-2011, in Explorer, Ranger, Mountaineer and Mazda B-Series trucks. Transtar also lists the same solenoid for the Isuzu/GM 4L30-E from 2000-2004, a reminder that it is a shared Bosch design. Before you order, match the two-blade connector, the mounting tab and the red nose screens to your old solenoid, or send us your year and VIN and we will check it. The later 2002-up 5R55W and 5R55S use a solenoid body instead and do not take this part; our 5R55 identification guide explains the difference.
If the pan shows burned material or the other solenoids are original, the six-piece 4R55E solenoid kit replaces the whole electrical side at once. A truck with worn bores needs valve body work, and the Sonnax 4R44E/5R55E Zip Kit covers the common wear points. You can also compare our 1995 4R55E TCC solenoid if converter lockup is part of the complaint.
| Fits | 4R55E |
| Part type | Pressure Control Solenoid |
| Condition | New |
| Brand | OEM |
| Reference | D56431A |
| Ships | From the USA |
| Warranty | 1-year |
The 4R55E itself was only built for 1995-1996. The same EPC solenoid number (D56431A, now Rostra A56431A) is listed for the 1997-2011 5R55E and the 4R44E and 5R44E, so it usually fits those trucks too. The 2002-up Explorer with the 5R55W or 5R55S does not use it. Send your year and VIN if you are not sure.
It is the catalog reference for the Bosch-built EPC solenoid with two red screens used in this Ford family. Transtar shows it superseded by Rostra A56431A, which carries the same transmission coverage.
Yes, both. The circuit defaults to high pressure, so an open coil or broken wire gives hard engagements and firm upshifts. A solenoid that is sticking or blocked with debris lowers line rise and causes soft shifts, a delayed Reverse and converter slip.
No. The EPC solenoid mounts on the valve body, so you drain the fluid, drop the pan, unbolt the bracket and swap the solenoid. Plan on a new filter and pan gasket while the pan is off.
Use the MERCON-type automatic transmission fluid called for in your owner's manual and check the level hot with the engine running in Park. Do not mix in universal additives to fix shift feel.
If the transmission has high miles, burned fluid or debris on the solenoid screens, replacing the whole set with a solenoid kit is cheaper than a second pan drop. On a clean unit with one EPC code, the single solenoid is usually enough.
