All-new diesel and gasoline engines and the need to manage the increased horsepower and torque they produce were the driving factors behind Ford’s new 6R140 heavy-duty TorqShift six-speed transmission for 2011 F-Series Super Duty trucks. According to Al Bruck, Super Duty 6R140 transmission engineering manager, the new transmission was designed to deliver power quickly and seamlessly while maximizing fuel economy in a wide range of tough applications.
According to Ford, creating a transmission to serve both diesel and gasoline engines in a Super Duty application was a challenging proposition because the gearbox needs to deliver the substantial low-rpm torque produced by the diesel engine and efficiently use the higher rotational speeds of the gasoline engine. Ford engineers opted to use proven transmission architecture, but adapt it for heavy-duty use.
Ford’s 6R140 TorqShift transmission uses a Lepelletier-style powerflow, a technology used in rear-wheel-drive vehicles but typically not with larger diesel engines. The Lepelletier architecture reduces the complexity in connecting the gearsets and clutches. The six speeds require only five clutches, and the speeds of the clutches relative to one another are low, increasing the system’s efficiency.
To handle the torque of the 6.7-liter Power Stroke V-8 turbocharged diesel, Ford strengthened the system by employing a powder-metal carrier in the compound Ravigneaux planetary gearset. The carrier consists of four pressed powder-metal components sinter-brazed together to form a rigid power-dense structure. This solution ensures robustness and makes the architecture compatible with both the diesel and gasoline engines. A Ford-patented rocker one-way clutch is integrated with the carrier and helps improve 1-2 shift quality through the gearset.
A deep first-gear ratio and two overdrive gears create a wider ratio span. This, combined with available lower-axle gear ratios and a control system that automatically selects the most efficient shift schedule, helps provide the best combination of pulling power and fuel economy.
“The six ratios we’ve selected provide greater overall span and better overdrive performance, which reduces engine speed in highway conditions and improves fuel economy,” Bruck says. “Because we have six gears, we make smaller steps gear to gear, which helps keep the engine in its sweet spot in terms of performance and efficiency.”
Bruck says the 6R140’s TorqShift six-speed transmission balances convenience and control by automatically shifting during routine operation and also allowing full manual control. It features SelectShift Automatic transmission functionality, which includes both Progressive Range Select and manual functions.
With Progressive Range Select, a toggle on the shift lever allows the customer to reduce the range of available gears while in Drive. When the customer “taps” down into Range Select mode, the display shows the available gears and highlights the current gear state. This feature allows the driver to limit use of upper gears when heavily loaded or towing on grades.
Other features include standard enhanced Tow Haul capability, which provides better control when hauling a heavy load or towing a trailer, and a segment-exclusive Live Drive Power Take Off.