Ford 6R140

Ford's heavy-duty six-speed automatic, introduced for 2011 behind the 6.7 Power Stroke and carried through the Super Duty range until the ten-speed took over for 2020.

It is a clean-sheet design rather than a developed 5R110W, which is the thing most worth knowing when sourcing parts: the five-speed TorqShift it replaced shares very little with it. Ford kept the TorqShift name across both, and that name alone will not tell you which gearbox a truck has — the gear count will.

Its input rating is quoted at 1,400 lb-ft and that figure is routinely misread. It is the torque at the gearbox input, after multiplication through the converter — it is not a 1,400 lb-ft engine rating, and treating it as headroom for a tune is how these are broken.

The ratios run 3.974, 2.318, 1.516, 1.149, 0.858 and 0.674, which is the part that gives the truck its character: two overdrives, so sixth is a genuine cruising gear rather than a tall top. Reverse is 3.12. It is a one-piece aluminium case weighing around 325 lb dry, and it carries a live-drive power take-off provision and low-speed converter lockup — both features aimed squarely at towing rather than at economy.

It takes MERCON LV, and on a truck that works the filtration system is the maintenance item that actually matters: this unit was given a high-capacity filter because the duty cycle demands it.