Downshifting while slowing down in Tow/Haul Mode

Another JR · September 15, 2022

By “aggressive” I think the OP means the selection of a gear that results in very high rpm as opposed to the characteristics of the actual shift from gear to gear. That’s what I was commenting on, at least. It actually shifts very smoothly. I just don’t like descending with the engine revving at over 5k. The highest rpms my truck has seen in its 6500 mile life were the one time I put it in tow haul on a moderately steep mile half mile hill near my house just to try it.

Ray Pickle · September 15, 2022

8 hours ago, Another JR said:

By “aggressive” I think the OP means the selection of a gear that results in very high rpm as opposed to the characteristics of the actual shift from gear to gear. That’s what I was commenting on, at least. It actually shifts very smoothly. I just don’t like descending with the engine revving at over 5k. The highest rpms my truck has seen in its 6500 mile life were the one time I put it in tow haul on a moderately steep mile half mile hill near my house just to try it.

I don't recall my truck ever downshifting while in tow haul to 5k. Frankly I don't think it downshifts far enough at hwy speeds during deep descends to maintain desired speed. Example, if I have crested a hill and it is 5-6% down for the next mile plus and I am at 65mph the truck only downshifts to 4th gear in an attempt to hold speed. Often speed increases and a downshift to 3rd is no longer an option even on manual mode. If I am concerned about the length and steepness of the decline I typically slow to about 50 or 55 and manual go to 3rd gear beginning descent. Rpm's are higher but truck is in control of trailer and brakes are cool if needed.

Sierra Jon · October 3, 2022

I regularly tow a TT that weighs 10k. Personally, the downshift works perfectly. I generally tap the brake when I know I am going to slow down and she immediately downshifts. It's like we're dancing. Haha

Also, I may or may not have used it when putting around town and that downshift gets my magnaflow to sputter a teeny bit when you coast down to 20mph. Music to my ears.

Dr1ft3r · January 29, 2023

On 9/15/2022 at 9:23 AM, Ray Pickle said:

I don't recall my truck ever downshifting while in tow haul to 5k. Frankly I don't think it downshifts far enough at hwy speeds during deep descends to maintain desired speed. Example, if I have crested a hill and it is 5-6% down for the next mile plus and I am at 65mph the truck only downshifts to 4th gear in an attempt to hold speed. Often speed increases and a downshift to 3rd is no longer an option even on manual mode. If I am concerned about the length and steepness of the decline I typically slow to about 50 or 55 and manual go to 3rd gear beginning descent. Rpm's are higher but truck is in control of trailer and brakes are cool if needed.

This sounds exactly like my recent situation while cruising down a 7% grade for 10 miles. My CC was set at 65 mph and I had to keep tapping the brakes because I kept creeping up to 70+ mph. I wasn't hauling and wasn't using tow mode. I think it was downshifting but it wasn't enough to keep my truck from accelerating by about 1 mph per 5 seconds. My truck is fat though with a curb weight of 7,450, lol.

As for the OP's issue: the downshift may seem aggressive for putting around town on flat land with a mild load. But you'll be thankful for that aggressiveness on a very steep grade with a full load. If it's too aggressive then just don't use it. You'll be using the sand pits if you need it and you don't have it.

Edited January 29, 2023 by Dr1ft3r

swathdiver · January 30, 2023

On 9/3/2022 at 9:36 AM, Epsilon Plus said:

I wouldn't be surprised if GM retuned it to be super aggressive after the crap showing in 2020 on TFL's Ike Gauntlet. The truck barely downshifted at all for them. My 2022 will drop gears like a professional trucker trying to brake an 80,000lb load (not a complaint, works great).

TFL doesn't use the cruise control while running the test downhill.

NaturallyAspirated · January 31, 2023

FWIW my truck is very unpredictable on the downhills. I’d like to better understand how GM’s CC is Supposed-to behave…

Ya at times it makes me feel like a boss trucker but other times I end up going 80 downhill like the OP.

swathdiver · January 31, 2023

7 hours ago, NaturallyAspirated said:

FWIW my truck is very unpredictable on the downhills. I’d like to better understand how GM’s CC is Supposed-to behave…

Ya at times it makes me feel like a boss trucker but other times I end up going 80 downhill like the OP.

What year is it? I wonder if it's described better in the Upfitter Manuals?

XY74 · January 31, 2023

I have also read the owners manual and am fine with their advice to use tow haul when loaded at 75%+, and not use it with less. I almost never use it. (disclaimer, I have a diesel with the 10 spd) What do you feel tow haul mode is giving you that you would miss aside from the aggressive downshifts when slowing? I wouldn't consider a 5000 lb boat to be too serious of a load for these trucks.