Owners manual info GMC

I often use it running empty in hilly areas with 35-45 mph speed limits. It stops the lugging which is never good for an engine.

Rover_Bill wrote:
It is my understanding that Tow/Haul mode keeps (or delays) your computer controlled transmission from up-shifting into the top-most gear when on the highway, delays (or slows) up-shifting in the lower gears when in stop-an-go traffic, and reduces gear hunting when driving in hilly terrain. All of these have a negative effect on your fuel mileage when not actually hauling a load and therefore not recommended in the owners manual.

The OP is talking about never using Tow / Haul, even when towing. :R Contrary to what the OP claimed, GM's position is that using Tow / Haul is beneficial if you're towing at 75% or greater of the vehicle's GCWR, not it's GVWR as the OP claimed. Heck, I'm towing a small 19' travel trailer that on average weighs ~ 4800 lbs loaded & ready to camp yet once I plug the numbers into my towing calculator it tells me that I'm towing at an average 74.15% of my Silverado's GCWR. If I were towing a popup I'd not bother but since I'm not I use Tow / Haul every time I tow our travel trailer. ;)

nevadanick wrote:
I bought a 2018 GMC 2500 dsl a couple days ago and today was reading the owners manual. In it about towing it said not to use tow/haul unless you were at 75% or more of gcwr. It said it was of no benefit and could cause you to use more fuel. I personally have never used tow/haul unless the trans was hunting between gears in all the trucks i have owned.

Hey guys maybe give the OP a break. His original post said GCWR, not GVWR!!

I'm going to assume the second post stating GVWR is a typo.

Yes i made the mistake of gvwr instead of gcwr. Sorry . How do i delete the post, i was just trying to pass on info that i had not seen before and i have had a couple of GMC's since 2011 and missed it in those manuals. Actually i just looked at my op and i had it right, forgot everyone on here already knows everything, bye.

nevadanick wrote:
Yes i made the mistake of gvwr instead of gcwr. Sorry . How do i delete the post, i was just trying to pass on info that i had not seen before and i have had a couple of GMC's since 2011 and missed it in those manuals. Actually i just looked at my op and i had it right, forgot everyone on here already knows everything, bye.

No problem. I think most got the point you were making. So does the GM have the grade braking algorithm in the transmission all the time? Or does it only come on with tow/haul?

on my 2015 denali duramax, using tow haul the 5-6 shift occurs around 62-65 mph. so in tow haul I'm often in 5th rather than 6th.

So, I usually don't use tow haul. I do use it going downhill or up steep grades. downhill with tow haul and exhaust brake works better than non tow haul and exhaust brake.

I'd say the GM info is reasonably accurate, at least with the duramax. In many cases tow haul isn't offering any big advantage.

mich800 wrote:

nevadanick wrote:
Yes i made the mistake of gvwr instead of gcwr. Sorry . How do i delete the post, i was just trying to pass on info that i had not seen before and i have had a couple of GMC's since 2011 and missed it in those manuals. Actually i just looked at my op and i had it right, forgot everyone on here already knows everything, bye.

No problem. I think most got the point you were making. So does the GM have the grade braking algorithm in the transmission all the time? Or does it only come on with tow/haul?

grade brake, at least on my 2015 is active all the time, but way more aggressive in tow haul. when not in tow haul using cruise control, it may not keep your speed down, even with the exhaust brake on has been my experience. with exhaust brake AND tow haul, your set.

Down hill or steep uphill grades is when I use tow haul. on level ground, rather not.

spud1957 wrote:

nevadanick wrote:
I bought a 2018 GMC 2500 dsl a couple days ago and today was reading the owners manual. In it about towing it said not to use tow/haul unless you were at 75% or more of gcwr. It said it was of no benefit and could cause you to use more fuel. I personally have never used tow/haul unless the trans was hunting between gears in all the trucks i have owned.

Hey guys maybe give the OP a break. His original post said GCWR, not GVWR!!

I'm going to assume the second post stating GVWR is a typo.

No kidding. Some people like to overreact to minor details and are so caught up in arguing over nothing they can’t see the intent of the post or obvious typos.

Thanks for the info, OP. So many on here insist that ANY towing or hauling means push the button and like to belittle those who “don’t seem to get that.” With lighter loads, T/H is just stupid aggressive.

It is an automatic folks !!!!

These threads always says to me...to ask/comment that these folks should have purchased a manual tranny so that they won't have these question and/or manage it themselves...as an 'automatic' is to manage the shifting between the gears for the human driver...

If you don't like the shift algorithms set by the OEM engineers...then get a tuner and either select their dialed in shift algorithms...or find one that has user programmable tables (algorithms) that suits

Here's the full text from my 2018 manual, so people see the exact and complete wording GM uses:

Tow/Haul is designed to be most effective when the vehicle and trailer combined weight is at least 75% of the vehicle's Gross Combined Weight Rating (GCWR). See “Weight of the Trailer” under Trailer Towing 0 296. Tow/Haul is most useful under the following driving conditions:

. When pulling a heavy trailer or a large or heavy load through rolling terrain.
. When pulling a heavy trailer or a large or heavy load in stop-and-go traffic.
. When pulling a heavy trailer or a large or heavy load in busy parking lots where improved low speed control of the vehicle is desired.

Operating the vehicle in Tow/Haul when lightly loaded or with no trailer at all will not cause damage. However, there is no benefit to the 318 Driving and Operating selection of Tow/Haul when the vehicle is unloaded. Such a selection when unloaded may result in unpleasant engine and transmission driving characteristics and reduced fuel economy. Tow/Haul is recommended only when pulling a heavy trailer or a large or heavy load.


I'm at 70% of my GCWR but with 15000 lbs of trailer, I use tow/haul.