Tow/Haul Mode: What It Does and Whether It Hurts to Leave It On

Ford's Super Duty owner's manual gives the most precise published account of what the feature does. It lists three things: > The tow/haul feature: > - Delays upshifts to reduce the frequency of transmission shifting. > - Provides engine braking in all forward gears, which slows your vehicle and assists you in controlling your vehicle when descending a grade. > - Depending on driving conditions and load conditions, may downshift the transmission, slow your vehicle and control your vehicle speed when descending a hill, without pressing the accelerator pedal. The amount of downshift braking provided varies based upon the amount you press the brake pedal. Chevrolet describes the same primary mechanism in its Trailering Guide: tow/haul "adjusts the shift schedule in the automatic transmission so it isn't 'hunting' for the correct gear while towing or trailering." So the honest summary is that tow/haul is mostly a different shift schedule, plus an engine-braking strategy on descents. Both manufacturers say the same two things. One extra Ford note worth knowing if your truck has it: on vehicles with the Adaptive Steering System, engaging tow/haul "reduces vehicle sensitivity to steering inputs at higher vehicle speeds" while keeping low-speed manoeuvrability. That is a real, published effect, but it applies only to trucks with that option.

These come up constantly in forum threads and video titles, and neither survives a check against manufacturer documentation. "It locks the torque converter earlier." No manufacturer document we could obtain states that tow/haul changes torque-converter lockup scheduling. It is a plausible-sounding mechanism, and it may even be true on some transmissions, but it is not something any of Ford's, GM's or Ram's published material claims. We are not going to assert it on their behalf. "It remaps the throttle." This one is narrowly true and widely over-generalised. GM states that tow/haul "adjusts the pedal map, steering, active rear steer, suspension and Traction Control System performance" — for the Silverado EV. In the same document, the description for the conventional Silverado, Suburban, Tahoe and the rest is limited to the shift schedule. Ford's F-150 marketing copy says tow/haul "improves power delivery", which is a claim about outcome rather than a described mechanism. If a truck's throttle does feel different in tow/haul, that is a real perception — but delayed upshifts alone change how the truck responds to the same pedal input, because you are sitting in a lower gear at the same speed. You do not need a remapped pedal to explain it. Why be this fussy? Because the same forum threads that confidently explain converter lockup also confidently explain that leaving tow/haul on will damage your transmission. Sorting the sourced claims from the plausible ones is the whole point of the next section.

This is the most-asked question about the feature, and the manufacturers answer it more clearly than the internet does. No manufacturer document we could reach says it is harmful. We searched the full text of Ford's 666-page Super Duty owner's manual, Ford's RV & Trailer Towing Guide, Chevrolet's Trailering Guide and Ram's towing basics material for any statement that tow/haul should be switched off, or is discouraged, when the vehicle is not towing. There is none. None of them warns of mechanical wear, transmission damage or drivetrain harm from using it unladen, and none quantifies a fuel-economy penalty for doing so. There is exactly one published prohibition, and it is not about towing at all. Ford's manual carries this warning twice — once in the Transmission chapter and again in the Brakes chapter: > WARNING: Do not use tow/haul when the road surface is slippery. Failure to follow this instruction could result in the loss of control of your vehicle. That is the rule that actually matters. Engine braking sends a retarding force through the driven wheels; on ice, snow or wet leaves that can break traction and swing the back of the vehicle around, and it does so without any brake lights or ABS intervention to warn you. The same warning appears alongside diesel engine exhaust braking for the same reason. Turn tow/haul off in slippery conditions, towing or not. On fuel economy, Ford says the opposite of the folklore — at least while towing. Its manual instructs: > If your transmission is equipped with a Grade Assist or Tow/Haul feature, use this feature when towing. This provides engine braking and helps eliminate excessive transmission shifting for optimum fuel economy and transmission cooling. Note the scope carefully: Ford is describing use when towing, and gives fuel economy and transmission cooling as the reasons to use it. Unladen, the picture is different in principle — holding lower gears longer means higher revs at a given speed, which generally costs fuel — but no manufacturer publishes a figure for that, and we are not going to invent one. A practical detail that dissolves much of the worry: on the Super Duty whose manual is quoted above, the feature deactivates when you power down the vehicle, so "leaving it on" is not even a persistent state — you re-engage it each time. Check your own manual before assuming the same of a different Ford. GM's Silverado EV is the exception in the other direction: it stays active if the vehicle is restarted within four hours.

Towing anything substantial. Ford's instruction is unambiguous: use the feature when towing. Delayed upshifts stop the transmission cycling between gears every time the grade changes, and repeated shifting under load is what builds heat. Descending a grade. This is where tow/haul earns its place. Ford's manual describes downshift braking that scales with how hard you press the brake pedal, so the transmission does progressively more of the work as you ask for more deceleration. Chevrolet names the equivalent feature Tow/Haul Mode Grade Braking, which "assists in maintaining desired vehicle speeds when driving on downhill grades by using the engine and transmission to slow the vehicle." Using it downhill is not just about convenience — it is about keeping the service brakes cool. Brakes that are worked continuously on a long descent fade, and a faded brake pedal with a loaded trailer behind you is the failure mode that mountain runaway ramps exist for. Chevrolet's guidance for grades is worth memorising in full: crest the hill no faster than the speed at which you want to descend, and in the gear you expect will require little braking. Climbing a grade. Ford's guide says tow/haul "eliminates unwanted gear search when going uphill", which stops the truck hunting between two gears on a long pull. Stop-and-go traffic with a trailer attached. The reduced shift frequency makes the rig smoother and puts less cyclic load through the driveline. Heavy loads in the bed, not just trailers. The name says haul as well as tow, and the shift schedule is just as useful with a bed full of gravel as with a trailer behind. When not to use it: slippery surfaces, per Ford's warning above. That is the only published restriction.

The button does broadly the same job across makers, but the feature names around it differ, and the names matter when you are reading your own manual. General Motors publishes four separately named features in this area, and they are not interchangeable: * Tow/Haul Mode Grade Braking — included on Silverado 1500, Silverado HD, Suburban and Tahoe; uses engine and transmission to hold speed downhill when tow/haul is enabled. * Automatic Engine Grade Braking — standard on Blazer, Equinox and Traverse; commands downshifts automatically on a descent and returns to the normal shift pattern once the grade eases or you touch the accelerator. * Cruise Grade Braking — standard on Silverado 1500, Silverado HD, Suburban and Tahoe; the same idea, active while cruise control is engaged. * Diesel Exhaust Brake — on Duramax models, a variable-geometry turbo creates back pressure to slow the vehicle; it works together with tow/haul and the grade braking features. Ford pairs tow/haul with an integrated engine-exhaust brake on the 6.7L Power Stroke Super Duty. Ford's description is that the combination "helps eliminate unwanted frequency of gear shifting on steep uphill grades and allow engine braking to maintain or reduce vehicle speed" on a descent. Ram publishes an exhaust brake recommendation rather than a tow/haul specification in its towing basics material: an exhaust brake is recommended for 3500 pickup and chassis cab models pulling 10,000 lb or more. Tow/haul versus manually selecting a gear. Manual selection is a blunter instrument that does one thing very predictably: it caps the gear. Tow/haul is adaptive and responds to the brake pedal. On a long, steady descent many drivers use both — tow/haul engaged, plus a gear cap to stop the transmission upshifting at all. Ford notes that all transmission gear ranges remain available while tow/haul is active, so the two are not in conflict. Tow/haul versus an exhaust brake. They are complementary rather than alternatives. The exhaust brake works on the engine side, tow/haul on the transmission side, and on the trucks that have both they are designed to operate together. If your concern behind all of this is heat, that has its own guide: can towing damage a transmission covers what actually runs the temperature up and what to do about it.