In this issue of GEARS, we’re going to delve into the Ford 6R80 transmission and discuss some of the more recent and major changes that have taken place.
Ford began using the ZF6HP26 transmission in the 2005 Ford Expedition and Lincoln Navigator with the 5.4L engine. In subsequent years, this transmission, known as the 6R60/75/80, began showing up in Explorer, Mountaineer, F150, and Mustang vehicles.
- a four-element torque converter which houses a multi-disc lockup clutch
- 3 driving clutches — clutches A, B, and E
- 2 brake clutches — clutches C and D
- a Lepelletier planetary geartrain
…and a valve body assembly fitted with a Mechatronic control unit, which controls all hydraulic functions through the electronic shift solenoids, to control garage shifting, shift timing, and shift feel.
The Mechatronic module also includes an output shaft speed sensor (OSS), a turbine shaft speed sensor (TSS), a transmission fluid temperature sensor (TFT), and a transmission range sensor (TR).
- 3.5L Turbo V6
- 3.7L Ti-VCT V6 with twin independent variable camshaft timing
- 5.0L V8
- 6.2L V8
Along with these new engines, new features and changes were made to the 6R80. The biggest and most obvious change was the addition of a one-way clutch, designed to provide smoother 1-2 and 2-1 transitions, quicker downshifts, and improved fuel economy.
A new feature which might not be as obvious is the Automatic SelectShift capability, which shifts the vehicle automatically during normal operation, provides a progressive range select mode, and gives the driver complete manual control when desired. For progressive range select mode, a toggle on the shift lever lets the driver reduce the number of available gears in drive.
When the driver taps the toggle switch in the selector lever down into range select mode, an LCD screen in the dash indicates the available gears and highlights the current gear. This allows the driver to limit the use of upper gears when the vehicle is heavily loaded or while towing up and down grades.
Let’s take a look at these changes and features to see how they’ve impacted this transmission.
The addition of the one-way clutch required multiple changes to the transmission case, the C and D support and all of its components, and the rear planetary assembly.
Changes were also made in the valve body, the molded lead frame, and the wiring harness, plus changes to the computer strategy for control of the D clutch.
In previous models there were a number of complaints of harsh 1-2 and 2-1 shifts which Ford tried to solve by updating the PCM calibration. In this unit, Ford added a one-way clutch to the rear planetary assembly to provide smoother transitions from 1-2 and 2-1.
Adding the one-way clutch required changing the strategy for application of the D clutch and solenoid D (figures 1 and 2). In previous models without the one-way clutch, the D clutch applies throughout first gear. In the 2011-later models with the one-way clutch, the D clutch only applies until about 3 MPH; then the D clutch releases (figure 2).
In earlier models without the one-way clutch, SSD or VFS4 D/E clutch solenoid didn’t energize until 2nd gear. In the 2011-later models with the one-way clutch, the solenoid turns on at about 3 MPH.
The SSD or VFS4 D/E clutch solenoid is a normally high solenoid. This means the solenoid receives low current to apply the D clutch; about 50 mA. It releases the D clutch when the current is high; about 850 mA.
Modulating the D clutch release allows the one-way clutch to be the holding member. This helps cushion the 1-2 shift, since there’s no clutch release during the shift. It also helps minimize 2-1 coastdown feel since the D clutch doesn’t come back on until the vehicle is almost at a full stop.
Notice the lugs on the one-way clutch (inside the red circle) (figure 4): There’s one missing lug on the inner race, which sits at the 6 o’clock position in the case. This area of the case is also the seat where the bias spring goes; more about that in a later issue.
If you disassemble the one-way clutch (figure 5, 6, 7), you’ll need to install the springs and diodes into the outer race and hold them in place with assembly lube so the diodes compress the springs; otherwise it’ll be difficult to assemble and install the inner race in the outer race.
The one-way clutch also created the need for another dimensional change in the rear planetary carrier assembly (figure 8). Notice the difference in the height of the lugs between the two planetary carriers: The early planetary carrier without a one-way clutch had longer lugs; the late planetary carrier with one-way clutch has shorter lugs, to provide room for the planetary carrier.
So far we’ve been looking at the 2011-later 6R80E. We’ve covered why changes were made and some of the dimensional changes that were required to outfit this transmission with a oneway clutch. We also covered some of the strategy changes in clutch-and solenoid application. In the next issue we’ll cover the rest of the hydraulic and electronic changes; stay tuned!