4R100 Overhaul Kit

If a Ford Super Duty, Excursion or E-Series van with the 4R100 is leaving spots on the driveway, takes its time finding Reverse, or loses its grip on the 3-4 shift with a camper behind it, a reseal is usually the core of the fix. This is a new 4R100 overhaul kit, pictured in a sealed Transtec envelope. It is not tied to a single model year in the listing, which makes it the general-purpose kit for a 4R100 rebuild when the hard parts in your unit are confirmed good.

What the overhaul kit does in a 4R100

The 4R100 is a hydraulic transmission run by an electronic brain: the PCM sets line pressure through the EPC solenoid and selects gears through the shift solenoids, but every shift still depends on oil reaching a piston without leaking past a seal. The kit supplies the gaskets, piston seals, lip seals, O-rings and sealing rings for that path. Sonnax's 4R100 flow research showed how sensitive this unit is to oil volume at low engine speed, so a leaky circuit costs more here than in a light-duty transmission.

Symptoms

• External leaks at the pump, pan, case connector or extension housing
• Slow engagement into Drive or Reverse, worse when cold
• Slipping or flaring on upshifts that grows with fluid temperature
• Converter clutch shudder or cycling at low speed, which can come from low pump volume as much as from the converter
• Codes 62, 628 or 1744 alongside soft shifts, which Sonnax ties to regulator and modulator wear

How to confirm the cause

Before buying parts, rule out the connector. Transmission Digest names the E4OD/4R100 case connector as one of the most troublesome at installation, with a fragile lock tab and pins that corrode quickly. Then check line pressure and vacuum-test the valve body as covered in our valve body testing guide. Worn bores can mimic leaking seals, so the kit only helps if the leak is in the clutch circuits.

Fitment

This kit is listed for the 4R100 without a year range. The 4R100 went through running changes in the pump, coast clutch drum and converter clutch control, and PTO units differ from non-PTO units. Match the ID tag, or send us your year and VIN and we will confirm it. If you already know your year, the year-specific kits and hard parts are in the E4OD and 4R100 collection.

Install notes

• Clean the case passages and valve body with solvent and dry air before installing new gaskets.
• Pre-lube seals with MERCON V, size Teflon-style sealing rings before installing drums, and air-check each circuit.
• Inspect the overdrive one-way clutch and planetary while the unit is apart; a worn 4R100 sprag clutch causes a slip a reseal will not cure.
• Replace or flush the cooler. Debris from the old unit in a reused cooler is a common reason a rebuild fails early; an E4OD and 4R100 transmission cooler is a cheap insurance item, and our cooler line guide covers the lines.
• Install a new filter and fill with MERCON V, checking the dipstick hot.

Which years does this 4R100 overhaul kit fit?

It is listed for the 4R100 without a specific year. The seal set is common across most 4R100 units, but send us your year and VIN and we will confirm it before it ships.

Is this a master kit with clutches?

It is listed as an overhaul kit, the gasket and seal set, pictured in a sealed envelope. If the frictions are burnt, add a clutch pack or choose a master kit.

Can low fluid volume cause converter clutch problems?

Yes. Sonnax documented 4R100 converter clutch complaints caused by low pump volume at low rpm. Inspect the pump and valve body during the rebuild.

What fluid does the 4R100 take?

MERCON V. Check the level with the engine running and the fluid at operating temperature.

Why does my rebuilt 4R100 throw solenoid codes?

The case connector lock tab breaks easily and the pins corrode. Inspect and secure the connector whenever the solenoid pack is disturbed.

• E4OD Valve Body Symptoms and Testing
• E4OD Cooler Line Replacement Guide
• E4OD Common Problems and Fixes
• E4OD Pressure Control (EPC) Solenoid Symptoms