4R100 Overhaul Kit 1999, new and ready to install. Fits the 4R100. Ships fast from the USA.
A 1999 4R100 that is leaking, slipping when hot, slow to engage on a cold morning, or simply coming out for a rebuild after years behind a 7.3L Power Stroke or a V10 needs every seal in it replaced before it goes back in the truck. This new overhaul kit is that seal and gasket package for the 1999 4R100, the second model year of Ford's updated E4OD and the first year of the Super Duty trucks.
The 4R100 is a hydraulic transmission: the pump makes pressure, the valve body routes it, and each clutch only applies if its circuit holds. An overhaul kit restores that sealing. It covers the pan and case gaskets, the piston seals for each clutch, the sealing rings on the drums and shafts, and the O-rings throughout the unit. Overhaul kits for this transmission are normally the soft parts only; frictions and steels come in a master kit, so check the contents in the photos and order clutches separately if your packs are burnt. A tired seal set lets apply oil bleed off, which is why a 4R100 with hardened seals slips under load, flares between gears and gets worse as the fluid thins with heat.
Check fluid level and condition, then put a gauge on the line pressure tap and compare idle and stall readings to spec. Low pressure in every range points to the pump or a leak common to all circuits; low pressure in one range points to that clutch circuit. Pull codes so you are not rebuilding around a solenoid or sensor problem. Our E4OD and 4R100 common problems guide walks through the overdrive section failures and the pump and converter clutch codes, and the valve body testing guide covers the vacuum test that separates a worn bore from a seal leak.
This kit is listed for the 1999 4R100. That year the unit went into the new F-250 and F-350 Super Duty, F-450 and F-550 chassis cabs, E-Series vans, the F-53 motorhome chassis and the SVT Lightning, behind the 5.4L, 6.8L V10 and 7.3L Power Stroke. 1999 sits inside the 4R100's PWM versus on/off converter clutch split and the PTO versus non-PTO coast clutch drum split, and those change some internal parts. Match the kit contents to your teardown, or send us your year and VIN and we will confirm before it ships. Do not mix it with an E4OD build; the 4R100 vs E4OD guide explains why. All parts for this family are on our E4OD and 4R100 parts page.
Soak the new piston seals and lip seals in clean fluid before assembly and lube every sealing ring with assembly gel so it centers in its groove. Air-check each clutch circuit as it goes together, and recheck endplay before the pump is torqued, especially on PTO units where the drum rides on a bearing. While it is apart, replace the open-end overdrive piston ring with a locking ring and inspect the overdrive one-way clutch; a 4R100 sprag clutch for 1999-04 is listed if yours is worn. Finish with a new 4R100 filter and pan gasket kit, flush or replace the cooler so old debris does not return, and refill with MERCON V.
| Fits | 4R100 1999 |
| Part type | Overhaul Kit |
| Condition | New |
| Brand | OEM |
| Ships | From the USA |
| Warranty | 1-year |
Doing this repair right usually means replacing these at the same time. Same transmission, ships together.
Overhaul kits for this unit are the gasket and seal package. Frictions and steels are part of a master rebuild kit. Check the contents shown in the photos, and order clutches separately if your packs are worn or burnt.
Most sealing parts carry across the 1998-2004 4R100, but drum and pump revisions changed some pieces over those years. Send your year and VIN and we will confirm fitment before it ships.
No. The 4R100 changed the pump, coast clutch drum and converter clutch control, so buy the overhaul kit listed for your E4OD year instead.
Use MERCON V automatic transmission fluid, along with a new filter and pan gasket and a clean cooler circuit.
Frictions and steels if worn, the filter, a locking overdrive piston retaining ring, and any worn one-way clutch or bushings. Test the solenoid body and flush or replace the cooler before the truck goes back in service.
