Tow Using Manual Shift for Chevy Express 3500??

My owners manual says to only use Tow/Haul at 80% of GCWR. My opinion is that towing any high walled trailer should use tow/haul mode because pulling two sheets of plywood through the air is hard work. Heck, I prefer the shift points of tow/haul mode even when not towing.

Thanks guys!

I found a few articles last night that discussed "tow/haul" -- when it is best to use it and when it simply isn't necessary. Most stated unless you are really tugging a heavy load, you are OK without engaging it when traveling flat highways. The authors also recommend using it for for downgrades as well as stop and go city traffic. My TT is really light so I don't think I will need it most of the time. Had the van out in "manual" yesterday without towing and found it pretty easy to use. I'm heading out this weekend, a couple of hours out for a show so I'll have an opportunity to see how manual works when I'm towing and what my RPM's run in 5th and then in drive and compare the two.

First, consult the owners manual. It tells you when to use Tow/Haul mode and when to use M mode.

My wife in an engineer at GM now. I would not take her advice on towing from her, nor from that retired one.

Manual mode is nothing like manual gear selection. It just limits the automatic shifting of gears to never exceed the indicated gear. If the truck is in M5 going 30mph, you aren't actually in 5th gear. 3rd probably.

You won't want to tow under 2000rpm. The 6.0L doesn't have much power below 2000rpm. While it is plenty for an empty truck/van, not when when you double the weight the engine is trying to move. I like Tow/Haul mode and M5 most of the time when towing my TT. I like to stay between 2000rpm and 4000rpm most of the time. Peak torque of the 6.0L is over 4000rpm and it seems to wake up over 3000rpm.

Use tow haul mode any time you tow your TT. The pennies you may save on fuel will be blown on transmission repairs.

Here is what the Owner's Manual has to say on the subject:

[COLOR=]"The Tow/Haul Mode adjusts
the transmission shift pattern to
reduce shift cycling, providing
increased performance, vehicle
control, and transmission cooling
when driving down steep hills or
Mountain grades, towing, or hauling
heavy loads."

Sounds like a good idea to me.

Maybe a minor improvement as this is only when you are accelerating , once you are rolling its all the same .

First Tow Haul will raise the shift points, and lock the torque converter in the upper gears. Both of these are good things.
Have no experience with a 6L80 transmission, but you should be able to shift into and out of manual mode at any time. DW's car has manual mode and it will improve mileage slightly, not downshifting on grades.
Had a 04 truck with the 6.0L motor and a NV4500 5 speed. At least then you had to maintain 2500 to 3000 for towing up even a gentle grade. 3000-3500 for any real pull. Never felt the need to rev more for power.