From Mechanical Database
The Ford 4EAT-F is a 4 speed electronically controlled automatic transaxle with lock up. Introduced in 1990, by Mazda Motors, the F4A-EL or 4EAT-F was classified as a light duty transmission based on the Mazda GF4A-EL or 4EAT-G used in the Ford Probe and Mazda 626. The 4EAT-F has 120 FT-LBS torque capacity in its stock configuration. The original 4EAT-F was introduced by Ford Motor Company and used three electronic shift solenoids, one lockup solenoid and was shifted via a kick down cable. The kick down cable was removed in 1997 and replaced with an electronic pressure control or EPC solenoid and the transaxle was renamed the F4A-III. Over the years the 4EAT-F has manifested many flaws ranging from the lack of torque capacity to the front seal being forced out of its bore due to line pressure spikes.
On to the problems.
The first failure in the F4A-III starts long before it ever manifests itself. This failure is the most overlooked and often the most detrimental problem the transaxle has. It in fact, is a result of cheap engineering by the factory. The cause of failure is the thin aluminum thrust washer found inside the torque converter. As the washer wears it deposits fine aluminum particles in the transmission fluid and they are carried throughout the transmission. These particles are moved throughout the transmission often under pressure and start to wear out critical components. The small aluminum particles acting like a sandblaster attack the soft copper bushings, the teflon sealing rings and the rubber seals and gaskets causing internal leaks and loss of line pressure throughout the transaxle. The aluminum particles also degrade the the finish of the accumulator and valve body bores and cause shift feel problems and complaints. Lastly it is worth to note that the aluminum particles will mix with the carbon that is found in transmission fluid and creates what i will call Muck. This muck will be deposited throughout the transmission and eventually ends up in the valve body and accumulator and also the transaxle cooler and line assemblies. Note: when ever servicing, rebuilding a 4EAT-F or F4A-III transaxle it is important to always replace the stock ford torque converter with an heavy duty unit featuring a Torrington bearing, instead of a thrust washer, such as the ones sold by ZXRacing in the dealer section.
It is also important to flush the cooler lines and transaxle cooler assembly with a good cooler flush such as ATP's Transmission cooler line flush in can and dry with compressed air. Failure to clean the cooler and replace the converter will result in re-contamination of the new or rebuilt transmission.
Another common problem with the F4A-III is the shift shudder when shifting into 2nd gear. The shudder in second gear is a two part problem. The first problem is the quality and material of the bands used both at the factory and by rebuilders. OEM and common aftermarket bands are made of the standard tan materials and are prone to glazing. Once a band starts to glaze its surface hardens and it loses its holding ability and starts to slip this slip is what causes the shudder and shock felt in the 1-2 shift on most higher mileage F4A-III. The only way to prevent band glazing and 1-2 shift shudder is to use a Dakin (charcoal colored) 2-4 band. The second problem is the condition of the 2-4 band drum surface, this surface when in contact with a glazed band and high heat can burn and sometimes even warp the drum. Caution should be taken when rebuilding to check the surface for warpage and also to recondition it with a peice of 180 grit sand paper to remove any glazing and promote holding power.
The reverse bang or harsh reverse engagement, felt especially when going backwards up a hill, has and need not be an issue. There is a very simple fix that i will detail later.
A good thing to remember is the .010ths per friction rule for racing and heavy duty transaxles. At the factory the clutch pack clearances are set on the loose side generally allowing .020ths per friction to allow for soft comfortable shifts that your grandmother would like. The increased clutch pack clearances create longer shift times and and increased heat on the clutches. A tighter clutch pack clearance provides a firmer and more crisp shift with less heat generation.
Torque capacity itself is a problem with this transmission as stated before the transmission has a torque capacity of only 120 FT-LBS. This need not be the case there are several upgrade parts packages available that can increase the torque capacity of this transmission by 60%.
The F4A-III consists of five clutch packs, one band and two one way clutches. We will detail each clutch and its usage.
The Forward clutch consists of 3 frictions and 3 steels is applied in all forward gears and takes the most strain. When selected 33% of the engines torque is applied to each friction.
Low Reverse clutch consists of 4 frictions and 4 steels and is applied only and drive low and reverse. When selected 25% of the engines torque is applied to each friction.
The 3-4 clutch or Overdrive clutch consists of 3 frictions and 3 steels and is applied only in overdrive or drive four. When selected 33% of the engines torque is applied to each friction. This clutch is prone to failure due to heat and lack of friction area and should be upgraded to the 5 friction TorquePaK setup. This pack increases the torque capacity of the 3-4 clutch pack by 60%. With a 5 clutch pack setup 20% of the engines torque is applied to each clutch.
The Reverse clutch consists of 2 frictions and 2 steels and is applied only in reverse. When selected 50% of the engines torque is applied to each friction.
The Coast Clutch consists of 2 frictions and 2 steels and is only applied during coasting or periods of deceleration. When selected 50% of the engines torque is applied to each friction.
The 2-4 Band is applied in second and 4th gear. When second gear is selected the 2-4 band is applied and holds 100% of the engines torque. The when fourth or overdrive is selected the transmission is already as the 3-4 clutch applied and all that is needed is the application of the 2-4 band.
Another weak link in the 4EAT-F is the input sprag or one way roller clutch. The sprag has been know to explode literally and embed metal throughout the transmission. A heavy duty sprag is available for the 4EAT-F that will prevent the input clutch failure and increase torque capacity.
Common systems or problems and their fixes
A common problem with the 4EAT-F has been the valve in the pump sticking. Delayed engagements hot, especially reverse, neutrals at stops, 3rd gear starts until throttle is added, high clutch failure, and possible pump damage are all results of a malfunctioning pump valve. Be sure to closely inspect the pump body for metal transfer between the outer gear and the pump gear bore wall. Remember that all the oil, and metal particles, that are discharged from the pump will be routed to the pump valve. To greatly reduce valve sticking complaints and failures install a redesigned Pump Valve. This valve is improved over the factory design by having numerous cleaning grooves along the length of the valve. Sticking valve complaints are greatly reduced with the redesigned valve.
A complaint of slips on start-off in drive, may be worse hot, but works OK in manual second and low is most commonly due to a cracked forward drum housing. The crack is most easily seen from the back, bottom, side of the drum. If the vehicle is driven in drive and allowed to slip for any length of time the forward clutches will burn out. A cracked housing can also create 3-4 bind, burnt band, burnt coast clutch and/or chatter on 1-2 shift, depending how badly the housing is cracked.
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