Quote:
Originally Posted by rbryan4
I probably should have been more clear. There is no OD button. Its tow/haul, sport, or normal.
Tow / haul mode changes the shift strategy, and also raises the line pressure, to reduce the chance of slippage, causing heat buildup.
The older OD version simply turned off the OD.
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Tow/haul mode also holds the gears longer, and on longer downgrades it downshifts earlier, not unlocking the converter, which helps braking too.
Ford recommends using tow/haul mode whenever you tow, and I do.
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All great info.
Tow/haul mode usually keeps the torque converter clutch locked up more, too.
Quote:
Originally Posted by rbryan4
The new design, doesnt have OD, but another gear.
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Long ago, "overdrive" meant an extra two-speed gearbox after the main transmission, which had direct and overdrive ratios... sometimes electrically engaged. In cars and light trucks, those are long gone.
That "extra" gear is an overdrive ratio (output faster than input) - that's all that transmissions with an "OD" button or selector lever position have, as well. The difference between a transmission with overdrive lockout (OD button) and tow/haul mode is entirely in the control system, not the mechanical design. In a modern transmission the highest gear or two are usually overdrive, and the one below them is sometimes direct, with the rest being reduction ratios, but it really doesn't matter in any way unless you are into internal design of gearing systems. The F-150 has four reduction ratios (gears 1 thorugh 4) and two overdrive ratios (5 and 6), and no direct ratio... but all that matters is that there are six ratios available.
An "OD" button just keep the transmission from using the top gear or two... typically whatever gears are not covered by the selector lever.
Linear Mode
