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Automatic Transmission

Ford 6F50 – The Other Six-Speed Transmission

  • Author: Mike Riley
  • Subject: Ford 6F50
  • Issue: Upgrades

(What starts out the same may not end the same)

Part 2 of 2 Parts

When GM and Ford collaborated to develop the new FWD six-speed transmission family, the results differed due to design and suppliers used, and each company subsequently made different modifications.

GM designated its changes as Gen 1 or Gen 2, but the Ford changes were mainly designated by the month and year that they occurred. Before ordering replacement components for either transmission family, make sure to specify the precise application.

Beyond design changes to address component failures, improvements in shift strategy or even to cut manufacturing cost, both companies have model variations to accommodate torque capacity. The GM models are 6T70/6T75 and the Ford models are 6F50/6F55.

The second part of this two-part analysis begins with the low/reverse clutch.

Low/reverse clutch: Initially, the low/reverse friction plates were basically the same between Ford and GM transmissions and were the only tan plate used by GM. The friction was changed for the GEN 2 6T70 and can be identified by notches in the teeth. Ford, on the other hand, upgraded to a segmented friction design, also occurring in February 2012 (Figure 1). The amount of waviness between the friction plates can vary. The previous friction part number is 7T4Z-C and the new design part number is DT4Z-C.

From the start, the 6T70 used a low/reverse cushion spring whereas the 6F50 did not, at least until February 2012. At that point, Ford decided to add one (Figure 2).

The cushion spring part number is DT4Z-7E085-A and does differ from GM. When the cushion spring was added, both the low/reverse apply and backing plates were changed. To avoid clearance issues, use the correct plates:

  • Previous design:
  • Apply plate – 7T4Z-7B066-E
  • Backing plate – 8A8Z-7B066-A
  • New design:
  • Apply plate – DT4Z-7B066-B
  • Backing plate – DT4Z-7B066-A

Mechanical diode: The mechanical diode (OWC) in the 6T70 has remained fairly consistent, whereas Ford has changed the 6F50 diode several times, ending up with three possibilities. Two of the three part numbers contain the diode and a low/reverse backing plate (Figure 3A). The upgraded diode itself is the same for all three part numbers. To service previous models that does not require the low/reverse cushion spring use part number BT4Z-7A089-F. To service new models that use the cushion spring, purchase part number DT4Z-7A089-A. Both part numbers contain the specific backing plate. The upgraded diode without any backing plate is part number BT4Z-7A089-E.

One noticeable difference between Ford and GM applications has to do with the inner splines that contact the reaction planetary carrier teeth. The 6T70 diode splines are wide comparable to the planet teeth whereas the 6F50 diode splines are narrow, which results in a loose fit with the planet (Figure 3B). Amazingly, there is no clunking noise when putting the transmission into gear.

Output sun gear: Certain changes to hard parts can be somewhat minor, such as the output sun gear. To achieve better oil flow the bushing design of the sun gear was changed relating to the oil grooves (Figure 4). The OE part number for the upgraded design is AA5Z-7D064-A. It seems as though every little bit helps.

Input planetary carrier: There are other changes or upgrades to enhance torque capacity such as the input planet carrier. Both Ford and GM felt that five gears were better than four, so five gears were used for their beefier models like the 6F55 and 6T75 (Figure 5). The five-gear planet will drop into a unit that originally had a four gear carrier. Other components such as the drive pinion gear and differential ring gear are also heavier duty on the 6F55 models. The four-gear planet part number is 7T4Z-7D491-B and the five gear part number is AA5Z-7D491-B.

Valve body: Valve bodies and valve body components seem to change constantly on all transmissions, some more than others. Changes on the 6F50 to date have not been too brutal, although there has been some. An easy way to tell a Ford valve body from GM is by the valve body cover plate. The GM valve body has a heatsink for the internal TCM whereas; Ford doesn’t use it.

Ford did have an issue with certain vehicles from 2009 to 2011 relating to a low speed hesitation and harsh shifting condition that resulted in an upgraded main body separator plate. As a fix, one check ball was eliminated from the valve body and the corresponding hole in the separator plate was removed (Figure 6). When rebuilding a valve body, ensure that the right combination of components are used. A recalibration of the computer must be done after installing the upgraded separator plate. The part number for the new plate is BT4Z-7Z490-B.

Solenoid housing assembly: The biggest distinction between Ford and GM six-speed transmissions is that GM chose to go mechatronic (TEHCM) and Ford did not. The jury is still out as to which is the best approach. When a TEHCM unit is replaced on a GM transmission, it has to be programmed, or the engine may not even start – something that Ford is not afflicted with. There is, however, no free ride when replacing the solenoid housing on a 6F50 due to a specific solenoid strategy that must be programmed into the PCM. The correct solenoid I.D. and strategy numbers are located on the replacement housing (Figure 7). There is also a tag that comes with the replacement housing to aid in reprogramming. Although the solenoid housing part number has changed several times, the latest number is AA5Z-7G391-A which should fit most applications.

Internal mode switch: Early on, Ford did have an issue with the IMS creating a variety of application and shifting problems. As a fix, an upgraded IMS was released for service (Figure 8). When repairing an earlier model 6F50/6F55, it is advisable to replace the IMS as a precaution. The replacement part number is 9E9Z-7H557-B and will service all models.

Time will tell as to how much more stuff will be tweaked on Ford and GM six speeds, but it’s a sure bet that more will be.


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