GM tow/haul question

deerefan · Mar 26, 2007

My wife and I recently pulled our three horse trailer on a 2 hour trip, loaded with 3 horses, and averaged 13 mpg behind my 2005 Chevy Z71 w/ 5.3l. Of course, I had the truck in tow haul. One thing I noticed, especially coming home, was how much the truck downshifted. Now, I leave the trans in "D" and just push the tow haul button. Am I supposed to leave it in "3" so it won't shift into o/d and cause excessive heat in the tranny? I'm used to just turning the o/d off in my older trucks, not too used to this new tow/haul thing.

LoneCowboy · Mar 26, 2007

Just stick it in drive, press the tow/haul button go on with life.

The tow/haul tries very hard to keep your speed constant for you when slowing, so it downshifts for you. (really sweet in the mountains)

also, it won't go into a gear it doesn't like.

Casco1 · Mar 26, 2007

LoneCowboy said:
Just stick it in drive, press the tow/haul button go on with life.

The tow/haul tries very hard to keep your speed constant for you when slowing, so it downshifts for you. (really sweet in the mountains)

also, it won't go into a gear it doesn't like.

I agree 100% with LoneCowboy, I towed a 6 ton Toyhauler cross country last fall with Tow/Haul had no problems at all . I just put it in drive and let it do it's thing. It tends to shift at a higher RPM. The only thing I paid more attention to was the transmission temp guage.

deerefan · Mar 26, 2007

Thanks, that was what I was thinking, but needed a little reassurance.

MrJimi · Mar 26, 2007

What does your factory manual say about towing a heavy trailer.
It should be right
Jim

George2615 · Mar 26, 2007

Deerefan,
On my 05 Chevy the tow / haul mode is a push button on the end of the shift lever. Just touch it once for tow / haul mode. (probably the same as yours). To lock out overdrive I leave it in D and just push the button in and hold it a few seconds. The overdrive lockout symbol then lights up on the dash next to the tow / haul light. You should not tow heavy loads unless you lock out the overdrive as it will overheat the trans. The tow / haul mode raises the shift points while going through the gears so the engine isn't lugging. Try holding the button in longer and see if your O/D lockout light lights.

KAB · Mar 26, 2007

George2615 said:
Deerefan,
On my 05 Chevy the tow / haul mode is a push button on the end of the shift lever. Just touch it once for tow / haul mode. (probably the same as yours). To lock out overdrive I leave it in D and just push the button in and hold it a few seconds. The overdrive lockout symbol then lights up on the dash next to the tow / haul light. You should not tow heavy loads unless you lock out the overdrive as it will overheat the trans. The tow / haul mode raises the shift points while going through the gears so the engine isn't lugging. Try holding the button in longer and see if your O/D lockout light lights.

That only applies if you have an Allison Transmission. All other automatic transmission change the upshifts, downshifts, engage the Torque Converter Clutch from 2nd gear and up. (This is a summary statement.) It is recommended only to use Tow/Haul when the gross combined weight is 75% or greater.

Kurt

gemini5362 · Mar 26, 2007

I guess on my 06 with allison I would just put it in Manual mode and put the selector to 05 and push the tow button. That should lock out OD and have me in tow mode

KAB · Mar 26, 2007

Almost Correct - there are 2 overdrive gears on that Allison, but in Manual Mode you lose (with Duramax only) Grade Braking (unless you manually downshift - Tap the brake to have the tranny downshift) and Cruise Grade Braking (the vehicle will monitor speed while using cruise control and downshift accordingly to maintain speed)

Kurt