8F35 Master Rebuild Kit

Ford's 8F35 eight-speed transaxle sits in the 2019-and-newer Escape, Bronco Sport, Maverick and Lincoln Corsair, and by now many of those units are past warranty with slipping, harsh engagement, no-reverse or pressure complaints. When the teardown shows burnt frictions and hardened seals, this 8F35 master rebuild kit supplies the soft parts for the overhaul: friction discs, the valve body and case gaskets, piston and shaft seals, sealing rings and a filter, so the unit is resealed and every clutch pack gets new friction material in one job.

What the master rebuild kit does in an 8F35

The 8F35 is a compact front-wheel-drive eight-speed that reaches its ratios by applying combinations of clutches and brakes around its planetary sets, all controlled by a solenoid-heavy valve body. That design works on tight clearances and low-viscosity Mercon ULV fluid, so it depends on every seal holding pressure and every friction pack applying on time. When frictions glaze or seals harden, the PCM sees slip it cannot adapt out, shifts turn harsh or flare, and the debris ends up in the valve body. A master kit replaces the parts that wear out in every unit, giving a sound case and hard parts a fresh start.

Symptoms that lead to an 8F35 overhaul

• Slipping or flare in one or more gears, or a bang into Drive or Reverse
• Shudder, buck or jerk at low speed that did not go away with a software update
• Intermittent no reverse, or a reverse-related code such as P0766 that keeps returning
• No movement after a rebuild or converter swap, a classic pump drive problem in this unit
• Dark fluid with friction material or metal in the pan

How to confirm the 8F35 needs a rebuild

Ford has issued several bulletins on this transmission, and some of the most common complaints are fixed without an overhaul. TSB 21-2389 addresses a low-speed shudder with a PCM update, and TSB 19-2386 covers P0766 and intermittent no reverse caused by contamination at a separator plate orifice. Rule those out first. TSB 22-2281, for units built on or before December 20, 2021, traces slipping and harsh engagement to worn output planet carrier needle bearings, and that failure contaminates the whole unit. If the pan shows heavy wear material or the carrier has failed, the transmission needs to come apart. Our 8F35 problems and TSB guide breaks down each bulletin and which build dates it covers.

Fitment

This kit is listed for the 8F35 without a year split. Ford's 8F family started production in 2019 and includes the 8F24, 8F35, 8F40 and 8F57, which differ in solenoid layout and valve body casting, so a vehicle line can carry more than one variant depending on engine. Confirm your unit is an 8F35 from the transmission tag or your VIN before ordering, and compare the gaskets and seals to your parts at teardown. If you are unsure, send us the year and VIN. All the 8F35 parts we stock are in the 8F35 transmission parts collection. If you also want new steel plates, see the 8F35 master kit with frictions and steels.

Install notes

• Do not reuse the original output planet carrier on an affected build. TSB 22-2281 lists replacement carrier JM5Z-7N473-C.
• The pump drive gear and chain are not held in place during assembly and can drop out of position when the converter housing and torque converter go on, leaving a no-pressure, no-move unit. Hold them with the stator seal sizer, protect the turbine shaft seal, and install the converter with the transmission vertical. Ford tools 307-764 and 307-765 cover this.
• Inspect the planetary needle bearings, bushings and the critical wear areas Sonnax identifies for this unit, and vacuum test the clutch circuits before final assembly.
• Fill with Mercon ULV. Ford's fluid chart splits LV and ULV within some of the same vehicle lines, so verify the spec for your model year and engine.
• Clear adaptive tables and run the transmission relearn with a capable scan tool after the rebuild.

A bench holding fixture makes the carrier and pump work far easier; we stock the 8F35 bench mount fixture 307-769. Check the pump on the bench as well, and replace it with a 2019-2023 8F35 pump if the gears or drive chain are damaged.

Does this kit fit the 8F24 or 8F57?

It is listed for the 8F35. The 8F24, 8F35, 8F40 and 8F57 share a family design but differ in solenoids, valve body castings and internal parts, so confirm your tag or send us your VIN before ordering.

Does this kit include steel plates?

This listing is the friction, seal and gasket kit with filter. If your steels are heat-discolored or warped, choose our 8F35 master kit that includes both frictions and steels.

Why does my 8F35 not move after a rebuild?

The most common cause is the pump drive gear and chain dropping out of position when the converter housing or torque converter is installed. Pull the converter housing and inspect the chain and drive gear; damaged parts must be replaced.

What fluid does the 8F35 use?

Mercon ULV for most 8F35 applications. Ford's application chart lists LV in some lines and years, so check the chart or your owner's guide for your exact vehicle.

Should I replace the planet carrier during the rebuild?

On units built on or before December 20, 2021, Ford TSB 22-2281 identifies worn output planet carrier needle bearings as a cause of slipping and harsh engagement and supplies a replacement carrier. Inspect it closely and replace it if the bearings show wear.

Do I need to do a relearn after installing the rebuilt transmission?

Yes. Reset the transmission adaptive values and run Ford's adaptive learn with a capable scan tool, then drive through all gears so the PCM can relearn clutch fill times.

• Ford 8F35 Transmission Problems: What the Four Ford Bulletins Actually Say