[MCBuggyCo]

Many vans and pick-up trucks have a button with an image of a trailer on it. If you push the button a light comes on reading "Tow/Haul". What else changes?

[PalletJack]

All that the tow/Haul button does is change the way your transmission shifts. Your vehicle will be able to tow that car without any problems when the tow/haul button is engaged. When in this mode the transmission will shift at a later point, thus giving you more power.

[HotFr8Recruiter]

The "tow" or "trailer" button means the vehicle is equipped with a towing package for haulibg things like boat trailers. The button on mine changes the gear ratios elecronically to accomodate the extra weight of the trailer. I have a Chevy 1500 with an Allison trans.

It always amazes me that Chevy sells this as a pretty pricey item as a "towing package" on their Work Truck model, but does not include a hitch or lighting jack in the package.

Thanks,
HotFr8Recuiter

[dhalltoyo]

Tow/Haul (T/H) shift mode significantly changes the transmission's shift pattern to reduce shift cycling and to deliver better performance, control, and cooling when towing/hauling heavy loads.

For instance:

• Upshift points are raised at light to mid throttle position to use more of the engine's available power for accelerating.Downshift points are raised to enhance engine braking to help slow the vehicle.

• During deceleration, the torque converter clutch (TCC) remains applied at closed throttle to much lower vehicle speeds to significantly improve the effect of engine braking.

• During acceleration, the TCC is applied in 2nd range and remains applied in 3rd, and 4th. This improves the drivetrain efficiency and significantly lowers transmission sump temperature when towing heavy loads. In Normal mode, TCC generally applies only in higher ranges and is dependent on throttle position.

T/H can be used at any time, even when not towing. Some drivers may not like the T/H shift characteristics when the vehicle is lightly loaded, and thus normal mode would be selected. When not heavily loaded, some drivers switch from Normal to T/H mode during closed throttle downshifts from highway speeds to help slow the vehicle and then switch back to Normal mode after they've stopped. If the driver chooses not to use T/H when towing or heavily loaded, he/she can expect to see higher transmission sump temperatures, more wear and tear on the brake system, and increased shift cycling.


PS. Actually, you have the same power, using the Tow/Haul switch. Power defines the engine's work/time ratio. The engine's horsepower does not change.

Most machines are designed and built to do work on objects. All machines are typically described by a power rating. The power rating indicates the rate at which that machine can do work upon other objects. Thus, the power of a machine is the work/time ratio for that particular machine. A car engine is an example of a machine which is given a power rating. The power rating relates to how rapidly the car can accelerate the car. Suppose that a 40-horsepower engine could accelerate the car from 0 mi/hr to 60 mi/hr in 16 seconds. If this were the case, then a car with four times the horsepower could do the same amount of work in one-fourth the time. That is, a 160-horsepower engine could accelerate the same car from 0 mi/hr to 60 mi/hr in 4 seconds. The point is that for the same amount of work, power and time are inversely proportional. The power equation suggests that a more powerful engine can do the same amount of work in less time.

[piper1]

On many GM's (the Allison in the pickups and the 4L85 in vans and cutaways) the T/H mode will also raise line pressure in the transmission so the various clutches will apply with more force and slip less, hence the "firm" shift.

HotFr8Recuiter, are you sure you have an Allison in a 1500 and not the new 6L90 GM?