Tow Haul.......When?

Thanks for the explanation of the GM transmission operations back then. If that's the case then yes, I would recommend using Tow/Haul anytime while towing or hauling a heavy load. My '03 Cummins Ram's gear selector had "Tow/haul" by the button but it was still the old "O/D Off" function in the software for it's 47RE transmission. The software change didn't come until mid-year. It wasn't until I bought the F250 with it's true 5spd auto that I experienced a real Tow/Haul mode.

pappcam wrote:
Tow/Haul is always on when I'm towing. I'm not going to be arrogant enough to think I can out engineer my truck company's engineers.

I guess some people just need to have control of every little thing so if they want to tow with it off, all the power to them.

What about the fact that you can see where the grade ends or if there is another one coming and the "smart" truck cannot?

I often turn off T/H briefly because it is very aggressive about staying lower gears (usually a good thing), even when the hill has let up for good.

Hannibal wrote:
In 2003, tow/haul may have been the new name for O/D off. If tow/haul locks out O/D in the '03 GM as it did in some Rams in between O/D off and real tow/haul mode, it could affect fuel mileage and I would be inclined to turn it off on flat no wind roads.

The OP doesn't mention which engine/transmission he has in his 2500HD, but since he's towing 11,000 lbs I'm assuming he has either a Duramax or an 8.1 gas with the Allison transmission. Tow/haul both changes shift points and enables grade braking on this transmission. It does not lock out overdrive. On the 4L80E with the 6.0 gas, tow haul changes the shift points and also does not lock out overdrive, but there is no grade braking. The 4L80E selector has 4 positions, so to lock out overdrive you place it in "3". I used to have a 2500HD with the 4L80E and observed that the trans actually ran a little hotter with T/H engaged, but I never towed over about 6,000 pounds. FWIW, the manual recommends T/H for loads exceeding 75% of GCWR.

Tow/Haul is always on when I'm towing. I'm not going to be arrogant enough to think I can out engineer my truck company's engineers.

I guess some people just need to have control of every little thing so if they want to tow with it off, all the power to them.

Lower engine speed does not always mean less fuel used. In fact, for naturally aspirated gas engines with high load (like pulling two sheets of plywood through the air at 65mph) many drivers use the same or less fuel at higher engine speeds, like 3rd gear instead of 4th gear. Many people with older 4-spd trans trucks that change differential gearing to numerically higher and get the benefit of better throttle response, cooler trans temps, fewer shifts, and use less fuel

Hannibal wrote:
In 2003, tow/haul may have been the new name for O/D off. If tow/haul locks out O/D in the '03 GM as it did in some Rams in between O/D off and real tow/haul mode, it could affect fuel mileage and I would be inclined to turn it off on flat no wind roads.

It doesn't. On the '03 GM, you'll have your full range of gears available in T/H. It will raise the shift points somewhat (ie, in t/h, it won't shift to top gear until about 60 mph, where it might have upshifted at about 50 otherwise), but I'll shift in to all gears, including overdrive, if conditions are right.

Hannibal wrote:
In 2003, tow/haul may have been the new name for O/D off. If tow/haul locks out O/D in the '03 GM as it did in some Rams in between O/D off and real tow/haul mode, it could affect fuel mileage and I would be inclined to turn it off on flat no wind roads.

Tow Mode did not lock out the fifth gear on our 2001 3500 chev and to the original poster there is no good reason not to use TM when towing.

chevman

KD4UPL wrote:
A guy with a GMC asks about T/H and a Ford guy and Dodge guy tell him to leave it off! :h

Tow haul works great with the Allison trans. I always use it when towing and hauling (isn't that self explanatory?) and often when not towing to save my brakes. I just replaced the rear brakes at 190,000 miles, the fronts are still original at 193,000.
T/H with the Allison is not just simply locking out some gears. All the gears get used but the shift points change and automatic downshifting occurs when slowing down. There shouldn't be any loss of MPG on a level highway so no reason to turn it off.

I didn't see where anyone told him to do anything.;)

its on any time I tow...or haul....seems simple enough to me and thats what the manual (dvd) said to do.

Daryll

Always when towing the 5ver or when hauling a heavy load.