The tow/haul feature adjusts the tranny shift points. Like posted above, it will hold gears longer.

OVerdrive is 4th gear. Typically your tranny will shift out of lock up and lock up before it drops a gear. When teh TCC unlocks it generates tons of heat at highway speeds and towing. Enough heat to fry a tranny. The owners manual recommends towing in 3rd gear (drive gear on the selector) while towing. You will burn more gas and your torque converter will still lockup. However your tranny wont hunt for gears. This is the lazy mans, and the dealers way of avoiding stupidity, or a burnt out tranny.

If your tranny starts to hunt for gears, downshift or change your crusiing speed. Typically the tranny will hunt on hillclimbs, headwinds, or if your crusiing around a shift point. Simply altering your speed will remidy the hunting and save your tranny. Too many people buy into the commercials and think its a race when towing. Going fast while towing isn't the problem, its the stopping part that creates the problem. Slow down and control the load.


The most important part of the towing package is the auxilary tranny cooler.

 

More copy and paste for ya.
Tow/Haul Mode
Applies to the following models:

• 2000-2004 C/K Utility Models

• 1999-2004 Chevrolet and GMC C/K Pickup Models (Silverado and Sierra)

• 1999-2002 GMC S/T Utility Models (Jimmy and Envoy-Old Style)


PURPOSE


• Reduce the frequency and improve the predictability of transmission shifts when pulling a heavy trailer or a large or heavy load. This is most apparent in city traffic. Without tow/haul, the transmission may upshift on a closed throttle decel. With tow/haul, the transmission will hold the current gear on a closed throttle decel. This reduces upshifts and downshifts.

• Provide the same solid shift feel when pulling a heavy trailer or a large or heavy load as when the vehicle is unloaded.

• Improve control of vehicle speed while requiring less throttle pedal activity when pulling a heavy trailer or a large or heavy load.


ACTIVATION


• Tow/Haul is selected or de-selected via a switch on the end of the transmission shift lever for all models except the GMC Jimmy and Envoy, their switch is mounted on the shift console. A light on the instrument panel will illuminate to indicate that tow/haul has been selected.

• Tow/Haul must be reselected every time the vehicle is started (if desired).


FUNCTION


• Tow/haul is designed to be most effective when the vehicle and trailer combined weight is at least 75% of the vehicle's Gross Combined Weight Rating (GCWR).

• Operation of tow/haul in a lightly loaded or non-loaded vehicle will not cause damage. However, there is no benefit to the selection of tow/haul when the vehicle is unloaded, this situation will cause a firm shift. The tow/haul switch is not a performance switch.

• Selection of tow/haul when unloaded may result in unpleasant engine and transmission driving characteristics and reduced fuel economy. Tow/haul is recommend only when pulling a heavy trailer or a large or heavy load.

• Examples of altered shift speeds when in tow/haul:

- Minimum 1-2 shifts pushed out approximately 13 km/h (8 mph)

- Minimum 2-3 shifts pushed out approximately 24 km/h (15 mph)

- Minimum 3-4 shifts pushed out approximately 48 km/h (30 mph)

- Tow/haul only affects shift points below 88 km/h (55 mph).

Refer to vehicle Owner's Manual for further information regarding tow/haul mode.

 

Budlight presents real men of genius. The savvy tranny advice giver. The 4L60E Pro. Always there when you burn yourself with 285* fluid. Ready to grab a driveshaft at 6000 RPM and show you how a real man doesn't wince as the skin sears away.

Heres to you Mr. Hanr3 , enjoy a Budlight complements of 4low, cheers.

 

gotta love the comic relief here eh?