GMC Tow/Haul Mode and Auto Grade Braking Explained

Tow/Haul mode on a GMC Sierra changes the transmission shift pattern so the truck stops hunting between gears under load, and it switches on Tow/Haul Mode Grade Braking, which uses the engine and transmission to hold speed on a downhill. Auto grade braking is the same idea working without Tow/Haul selected: the transmission downshifts on a descent when you hold steady pressure on the brake pedal. Both exist to keep heat out of the wheel brakes, and on 2014-era trucks both can be switched off for the current drive by holding the Tow/Haul button.

What Tow/Haul Mode Changes

The 2024 Sierra 1500 owner's manual says Tow/Haul Mode adjusts the transmission shift pattern to reduce shift cycling, which provides increased performance, vehicle control, and enhanced transmission and engine cooling when driving down steep hills or mountain grades, when towing, or when hauling heavy loads. The 2014 manual words it almost identically.

In practice the transmission holds each gear longer, so a loaded truck isn't bouncing between two gears on rolling terrain. The same manual lists a few other changes:

• Steering and sway control. Trucks with Active Hydraulic Assist get a stiffer steering response, and Tow/Haul adjusts Trailer Sway Control, if equipped.
• Stop/Start. If the truck has it, the Stop/Start system becomes unavailable while Tow/Haul is active.
• Manual range. Pulling the shifter from D to L starts you in a lower range when Tow/Haul is engaged.

That last point is published as a chart. For the 10-speed automatic, the 2024 Sierra 1500 manual and the 2026 Sierra HD manual show the same values:

Gear when you shift from D to L	10th	9th	8th	7th	6th	5th	4th	3rd	2nd	1st
Range selected, Tow/Haul not engaged	L7	L7	L7	L6	L5	L4	L3	L3	L2	L1
Range selected, Tow/Haul engaged	L7	L7	L6	L5	L4	L3	L3	L3	L2	L1

Tow/Haul also has a memory. If the truck is turned off in Tow/Haul and restarted within four hours, the mode stays active. After that it starts in Normal Mode.

The Three Kinds of Grade Braking

"Auto Grade Braking" is a common name for the feature, but the owner's manuals reviewed here don't use it. They split grade braking into separate functions. All three assist "in maintaining desired vehicle speeds when driving on downhill grades by using the engine and transmission to slow the vehicle." They differ in when they are armed.

Manual name	When it is enabled	Where it is documented
Normal Mode Grade Braking	At every start, with Tow/Haul off (gasoline engine, automatic transmission)	2014 Sierra manual, Automatic Transmission section
Tow/Haul Mode Grade Braking	Only while Tow/Haul Mode is selected	2014 Sierra manual, 2024 Sierra 1500 manual
Cruise Grade Braking	When cruise control is active	2014 Sierra manual, 2024 Sierra 1500 manual

Normal Mode Grade Braking (the "auto" one)

A GM service bulletin on file with NHTSA (PIT5202B, July 2014) explains that it arrived on full-size trucks and SUVs for the 2013 model year, that it defaults to on after each ignition cycle, and that it needs the driver to apply steady brake pedal pressure on a downgrade before it steps in. Release the brake and the transmission holds the gear it picked. Press the brake again and it may downshift further. Pressing the accelerator exits it.

The first time it engages in a drive, the Driver Information Center (DIC) shows GRADE BRAKING ACTIVE. The bulletin adds that the Normal mode version downshifts less aggressively than the Tow/Haul version.

Tow/Haul Mode Grade Braking

Same behavior, only armed while Tow/Haul is selected. On the 2014 Sierra and the 2024 and 2026 Sierra 1500, the manual says it is not enabled in Range Selection Mode, so once you take over gear selection in M or L, the truck stops choosing downshifts for you.

The Sierra HD is different. The 2026 Sierra 2500 HD/3500 HD manual states that "Grade Braking is available in all modes, including Range Selection Mode."

Cruise Grade Braking

With cruise control set, Cruise Grade Braking downshifts to hold the set speed on a descent without any brake pedal input. The 2024 Sierra 1500 manual says it is enabled when the vehicle is on and cruise control is active. The DIC message does not appear for this one, according to the GM bulletin.

Where the Tow/Haul Button Is

The control moved between generations.

• 2014 Sierra: the manual puts the selector button on the end of the column shift lever. Press it to turn Tow/Haul on or off, and a light comes on in the instrument cluster.
• 2024 and 2026 Sierra 1500: Tow/Haul is part of Driver Mode Control. Press the Tow/Haul button at the mode knob. For trucks without Driver Mode Control, the manual says to press the Tow/Haul button on the center stack.
• 2026 Sierra HD: depending on trim, the Tow/Haul button may be on the drive mode control knob or on the center stack.

Layouts vary by trim. GMC's Manuals and Guides page has the correct PDF for your year and model.

How to Turn Grade Braking Off

On a 2014 Sierra with a gasoline engine, the owner's manual gives the same procedure for Normal Mode, Tow/Haul, and Cruise Grade Braking: press and hold the Tow/Haul button for five seconds. The change is made when you release the button, and the DIC shows GRADE BRAKING OFF. Repeat it and you get GRADE BRAKING ON.

Three details matter here:

• It only lasts for the current ignition cycle. Grade braking is enabled again the next time the truck is started.
• The hold time is quoted two ways. The 2014 owner's manual says five seconds. GM bulletin PIT5202B says three. Hold for the full five seconds, release, and check for the DIC message.
• Diesel trucks differ. On the 2014 Sierra with a diesel engine, the manual says Tow/Haul Mode Grade Braking is enabled or disabled by pressing the Tow/Haul Mode button itself, with no long hold.

The 2024 and 2026 Sierra 1500 manuals reviewed for this article do not describe a hold-to-disable step. What they do document is that grade braking is deactivated while the truck is in Electronic Range Select or Manual Mode. On a late-model 1500, selecting L and setting the range yourself is the documented way to take control, and leaving Tow/Haul off removes the Tow/Haul version. Check the manual for your model year before assuming the older button hold still applies.

When to Use Tow/Haul, and When to Leave It Off

The towing section of the manual gives a specific threshold: Tow/Haul Mode "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)." That wording appears in the 2014 Sierra manual and again in the 2024 Sierra 1500 manual. The 2023 GMC Sierra 1500 towing capacity breakdown covers how those ratings work.

GMC says the mode is most useful when pulling a heavy trailer or carrying a heavy load:

• Through rolling terrain
• In stop-and-go traffic
• In busy parking lots

The manual also says to use Tow/Haul when driving down steep hills or mountain grades, and recommends it for heavier trailers generally.

Running it empty will not hurt anything. The 2024 manual states that operating in Tow/Haul when lightly loaded or not towing "will not cause damage" but is not recommended, because it may result in unpleasant engine and transmission driving characteristics, heavy or light steering efforts, and reduced fuel economy.

Does Tow/Haul Mode Use More Fuel?

GMC's answer is that last phrase: reduced fuel economy when the mode is used lightly loaded or not towing. The manual publishes no figure, and the penalty depends on load, terrain, and how long the transmission sits in lower gears. Holding gears longer means higher engine speed for the same road speed.

Why Grade Braking Protects the Brakes

The Sierra manual's Hill and Mountain Roads section carries this warning: using the brakes to slow the vehicle on a long downhill slope "can cause brake overheating, can reduce brake performance, and could result in a loss of braking." Its instruction is to shift to a lower gear and let the engine assist the brakes.

Grade braking does that downshift for you. GM's bulletin states the purpose: it helps reduce brake temperatures and wear on the traditional braking system. Heat is what causes brake fade on disc brakes, so less time on the pedal means more braking in reserve at the bottom of the hill.

It is an assist, not a speed limiter. You still need the brake pedal on steep grades, and the trailer's own brakes have to carry their share. See how to use a GMC trailer brake controller and the Sierra trailer brake gain settings guide for that side of the setup.

Diesel Trucks and the Exhaust Brake

Duramax trucks add an exhaust brake on top of grade braking. On the 2024 Sierra 1500, the manual says that if the vehicle has a diesel engine, exhaust braking is automatically activated when Tow/Haul Mode is selected, and the system commands downshifts and uses the turbocharger to reduce vehicle speed when the brake is applied. For the heavy-duty trucks, the 2014 manual's advice is to "use the exhaust brake and Tow/Haul Mode for maximum grade braking," with full details in the Duramax diesel supplement. The hardware itself is covered in how a GMC exhaust brake works.

Yukon, Canyon, and Acadia

• Yukon and Yukon XL (2023 manual): Tow/Haul is a position on the Mode knob to the left of the steering wheel. It adjusts the shift pattern, steering, and Electronic Stability Control. Cruise Grade Braking is not enabled in Range Selection Mode. The same 75% of GCWR guidance appears.
• Canyon (2026 manual): Normal Mode Grade Braking is enabled when the vehicle is started and is not enabled in Range Selection mode. Tow/Haul is selected with the MODE knob or, on trucks with only Normal and Tow/Haul modes, a button on the knob or center stack.
• Acadia (2026 manual): the feature is called Automatic Engine Grade Braking, available for normal driving and in Tow/Haul mode, and deactivated in Electronic Range Select mode. On all-wheel-drive models, choosing Tow/Haul also engages All-Wheel Drive.

The Terrain has its own set of modes, covered in the GMC Terrain drive modes guide.

Frequently Asked Questions

What does Tow/Haul mode do on a GMC Sierra?

It adjusts the transmission shift pattern to reduce shift cycling, so the truck holds gears longer under load. It also enables Tow/Haul Mode Grade Braking for descents. A light on the instrument cluster shows when it is active.

How do I turn off grade braking on a GMC Sierra?

On a 2014 Sierra with a gasoline engine, press and hold the Tow/Haul button for five seconds, then release. The DIC shows GRADE BRAKING OFF. It stays off only for that ignition cycle. Later Sierra 1500 manuals do not list that step, but they state grade braking is deactivated in manual range mode (L).

Should I use Tow/Haul mode with a light trailer?

GMC says the mode is designed to be most effective when the combined truck and trailer weight is at least 75% of GCWR. Using it with a light load will not cause damage, but the manual does not recommend it and warns of reduced fuel economy and less pleasant shifting.

Is it normal for the engine to rev high going downhill?

Yes, when grade braking is active. The transmission downshifts so the engine can slow the truck, which raises engine speed, and the DIC shows GRADE BRAKING ACTIVE the first time it happens in a drive on trucks with that message. Pressing the accelerator returns the transmission to its normal pattern.