Best way to use tow haul with trailer

tomseeley · April 24, 2005

Newbie here. Just bought my first new used truck and new used travel trailer. 2002 GMC Sierra crew cab, 4x4, 2500HD, duramax/allison. Trailer is a 2002 Nash 25S; about 25' 6" (not incl. hitch); GVWR = 7,400#. Equalizer hitch. Prodigy brake controller.

Haven't weighed any of it yet but I plan to.

I towed the TT home yesterday, from Akron to Pittsburgh, with no issues at all! What a truck!

I know what the tow haul mode is in principle. I could easily tell what it was doing as I towed the trailer home, up and down hills, through small towns, and on the interstate.

It seemed to keep me in one gear LESS than the highest once I reached cruising speed of 55 mph or so, unless I flicked it off for a second (which let it shift into what I assume was 5th gear and drop the rpms to under 2,000) and then back on again. If I didn't do that, it seemed to stay in what I assume was 4th gear, and the rpms at around 55 mph stayed around 2,200 or so.

My question is this: Which is the best way to use tow haul? Should I just let it do its thing? I.e., turn it on and forget about it anytime I'm towing the trailer? Or should I try to get cute and probably outsmart myself!?

mcreyaufmiller · April 24, 2005

When towing that size trailer, your best bet is to turn the tow feature on and let the truck do what it is programmed to do. If you get on the highway, use your best judgment. If you are in OD and the truck continues to shift in and out, turn on the tow featuer, if it stays in gear, leave it alone.

Jester4736w · April 24, 2005

Tom... Just like Mcrey said, use your best judgement. I would use it like a very sensitive overdrive. When your creeping through towns and single lane roads click it on, when you get on a nice straight, smooth highway, click it off and let the rpms level off. But, like mcrey said if it is shifting an unnormal amount, click it back on again.

P.S. --- As simple as that question sounds, it is actually a very good guestion.

BlackSilver · April 24, 2005

Tom,

Turn it on and let it run. It's smarter than we are, and there is no good reason not to use it. The benefits go far beyond just changing the shift points of the transmission.

CougMan04 · April 24, 2005

Only time I use the tow haul on my 6.0 HD is when I have my trailer loaded. I have used it a few times with it unloaded and didn't notice much of a difference.

mmmikkke · April 24, 2005

I know what the tow haul mode is in principle. I could easily tell what it was doing as I towed the trailer home, up and down hills, through small towns, and on the interstate.

It seemed to keep me in one gear LESS than the highest once I reached cruising speed of 55 mph or so, unless I flicked it off for a second (which let it shift into what I assume was 5th gear and drop the rpms to under 2,000) and then back on again. If I didn't do that, it seemed to stay in what I assume was 4th gear, and the rpms at around 55 mph stayed around 2,200 or so.

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I'm with you, Tom. Use your head. Always use your head.

If it feels right, it is right.

You already seem to have the right sense of what tow/haul is for. It eliminates unnecessary shifts and makes quicker shifts to keep the clutches from getting any hotter than would happen in normal driving without towing. Those later shifts keep you higher in the torque band to help you with negotiating through traffic, but when it feels like it's time to hit top gear, flick it off and hit top gear. If the engine's laboring, turn it on and let it take you down a gear. That's why the button is on the shifter handle. It makes it possible to do just this kind of intelligent driving.

Happy cruising. Congratulations on picking a fine truck.

KyleBst264 · April 28, 2005

When I'm towing;

-I leave tow/haul off when on on the open road, or in light traffic and on the highway.

-I flick it on when coming up to an off-ramp.

-I mainly just use it when I'm on city streets, and in traffic. It makes it much easier on the trans and brakes when towing stop light to stop light.

Shooter_va · April 29, 2005

I usually keep it on the whole time towing unless I am on a flat stretch of highway for a long time.

GONZO · April 30, 2005

does the tow haul not let the alison go into top gear at all? i'm wondering why people turn off tow/haul on flat ground?

when i have the camper on and towing a trailer i just leave the tow/haul feature on all the time. if i'm on flat ground the trans feels like normal in OD. you only notice it doing it's thing when you get into the hills, so ijust leave it on.

bluenote · April 30, 2005

does the tow haul not let the alison go into top gear at all? i'm wondering why people turn off tow/haul on flat ground?
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Tow/Haul mode will allow the Allison to go into 5th gear, but it usually won't happen until you get up around 62 mph and are not still accelerating. I do the same as what several others have mentioned, leave it in tow/haul when towing, turning it off for just a couple of seconds to allow it to shift into 5th gear when I'm towing at less than 62 mph.

The advantages of using tow/haul mode are many. Several are mentioned above, but in addition, it locks the torque converter in all gears except first. It also engages the full grade-braking feature, which will force 5-4, 4-3 and 3-2 downshifts as needed to maintain speed on downgrades, or assist in braking when coming to a stop.

mmmikkke · April 30, 2005

does the tow haul not let the alison go into top gear at all? i'm wondering why people turn off tow/haul on flat ground?
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Tow/Haul mode will allow the Allison to go into 5th gear, but it usually won't happen until you get up around 62 mph and are not still accelerating. I do the same as what several others have mentioned, leave it in tow/haul when towing, turning it off for just a couple of seconds to allow it to shift into 5th gear when I'm towing at less than 62 mph.

The advantages of using tow/haul mode are many. Several are mentioned above, but in addition, it locks the torque converter in all gears except first. It also engages the full grade-braking feature, which will force 5-4, 4-3 and 3-2 downshifts as needed to maintain speed on downgrades, or assist in braking when coming to a stop.

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That is cool. Thanks for the detail!