2011 Ford SuperDuty TorqShift six-speed automatic transmission; image courtesy Ford Motor Company. Click image to enlarge
By Jim Kerr
Ford’s new 2011 SuperDuty trucks have a new transmission: the 6R140 six-speed automatic transmission is built to reliably handle 735 lb-ft of torque from the new diesel engine while towing up to 11,068 kg (24,400 pounds) over rough worksites and rugged terrain. Read on for the details.
A Lepelletier-style gear arrangement reduces the transmission’s complexity. Only five clutches are needed for six gear ratios and new clutch materials add to the durability. A powdered metal carrier is used in the rear gearset and is made up of four separate parts sinter-brazed together to form the strong carrier. Looking at the gears it holds, they appear large and robust. Combining the front and rear gearsets in various combinations enables six forward speeds with a wide range of gear ratios. First gear is very low for strong off-the-line performance, and the top two gears are overdrive ratios for better fuel economy.
Other mechanical features include an optional live Power Take Off (PTO) drive. The PTO gear inside the transmission is connected to the torque converter, so it turns all the time the engine is running. PTOs are used to drive accessories such as hydraulic pumps, which in turn can operate snowplough blades, winches or tilting boxes. Now the driver can operate these features while the truck is moving, which is the advantage of a live PTO.
The torque converter includes a long-travel heavy-duty torsional damper spring as part of the torque converter lockup clutch. The torque converter can now lock up at very low engine speeds. Without this style torsional damper, engine pulsations would transfer through the drivetrain. Now, better fuel economy is achieved by locking the converter up as low as 900 rpm. This also reduces heat in the transmission, a move that will extend its service life.
While the mechanical features are critical, it is the driver’s control through the electronics that really impressed me. Ford’s “Select shift” shifter has two manual modes. First, the driver can lock out higher gears even when in Drive range by pressing the rocker button on the gearshift lever. This feature is great when you want automatic operation but only in lower gears, such as climbing or descending long hills.
Move the shift lever to the “M” position and you have full manual control of the gears. By pressing the rocker button, you can shift manually through all six gears and the transmission will remain in the selected gear at all times. If you select third gear, it will start out there, which could be useful on icy roads. If you try to select a gear that would overspeed the engine, the computer blocks the shift. Also, if you are going down a long grade and the engine speed approaches redline, the transmission will shift up to protect the engine, but a combination of big wheel brakes, engine braking provided by the diesel engine’s turbocharger closing down the exhaust flow, and the gear advantage of the transmission will prevent the engine speeds from increasing beyond what you want. Even on a six per cent downhill grade with 10,400 kg of trailer behind the truck, it was easy to control downhill speeds.
Transmission controls are programmed for smooth shifts under a wide range of load conditions. With no load, the transmission shifts as smoothly as that in a passenger car, and smooth shifting continues as loads increase. Only when towing at maximum capacity and while trying to accelerate quickly do you feel a firm shift and even then it is firm but not harsh. On long downhill grades, lightly touching the brake pedal will cause the transmission to smoothly downshift and hold the lower gear until the gas pedal is pressed.
Finally, the transmission can be put in tow/haul mode with the push of a button. This should be used when towing and modifies when and how it shifts, and internal hydraulic pressures, for better performance when the truck is loaded.
Reading these words, you may think that other transmissions do the same thing as this new Ford unit. You’d be partially correct, but my driving experience with this one highlighted the superb electronic controls mated to a strong mechanical gearbox. It performed better both loaded and unloaded than any other truck transmission I have driven and you hardly notice it doing it. That’s performance that sets a new standard for heavy duty transmissions.