4R100 Transmission Master Rebuild Kit w/ Raybestos Frictions

The 4R100 is the heavy-duty four-speed Ford put behind the 5.4 and 6.8 gas engines and the 7.3 and 6.0 Power Stroke diesels starting in 1998, when it replaced the E4OD. When one of these units comes across the bench for a rebuild, you strip out every gasket, seal, and friction plate and start clean. This kit is the soft-parts side of that job in one box: a full 4R100 overhaul kit plus a Raybestos friction clutch module so the unit goes back together sealed and holding pressure.

The overhaul portion covers the case and pump gaskets, the metal-clad lip seals, the Teflon and cast-iron sealing rings, and the full run of O-rings and square-cut seals that live in the drums, servos, and valve body. The Raybestos friction module (part RCP96-091) adds the 24-tooth reverse and 32-tooth overdrive friction plates, the two clutch packs that take the most abuse in a loaded Super Duty. Manufacturer part number on the complete kit is W36004EGW.

Fitment is the 1998-and-up 4R100 found in F-250, F-350, F-450, and F-550 Super Duty trucks, the Excursion, and E-series vans, in both two-wheel and four-wheel drive applications. One honest note before you order: this is an overhaul-and-friction package, so the steel separator plates are purchased separately. If your old steels are clean, flat, and not blued from heat, most builders reuse them; if they are heat-damaged, add a steel set to the order.

On the bench, air-check each drum after you assemble the new frictions and lip seals, set your clutch clearances to spec before the final stack, and pre-soak the new frictions in ATF so they do not glaze on first apply. Do the soft parts once and do them all at once. This kit keeps you from chasing a leak or a slipping clutch two weeks after the truck leaves.