How To Use 4×4 On A GMC Sierra


The GMC Sierra isn’t the first pickup you might think of when you think of offroading. General Motors, GMC’s parent company, has promoted this brand more for luxury than hard work.

But, this doesn’t mean the Sierra can’t tackle challenging terrain. In fact, these trucks have enough to take you anywhere. Let’s discuss how to use the 4×4 on a GMC Sierra

How To Use 4×4 On A GMC Sierra

Engaging the 4×4 on a GMC Sierra is easy. There’s a knob on the left side of the driver’s controls that allows choosing between Two-High (2H), Four-High (4H), or Four-Low (4L).

Some GMC Sierras come with the Automatic 4H, which sends torque to the front axle when it senses less traction. The situations in which you select each mode vary. 

To engage 4H, you can turn the knob while on the move. But, to use 4L, you must come to a complete stop. Then, you must shift into neutral before you turn into low range (from either 2H or 4H), and only then can you active 4L. 

You might have seen the terms High and Low in other trucks and SUVs. They refer to the range in which the gears are. 

The High-range option has a gear ratio that’s ideal for highway and general driving conditions. In it, the Sierra has lower torque but can reach higher speeds. 

On the other hand, the Low-range setting has a higher gear ratio. This increases torque but decreases final speed. We’ll explain this difference in more detail in another section. 

The Automatic 4H alternates between 2H and 4H, and it’s ideal for when you’re alternating between surfaces with good and bad traction. Contrary to the regular 4H option, you can drive with this option on most surfaces without damaging your vehicle. 

But, before we get into the ideal conditions for each mode, let’s talk about 4WD systems. Though they can be complex, it’s essential to understand how they operate. Doing so will avoid damage to your vehicle. 

What Is A 4WD System?

A 4WD system allows the driver to send power to all four wheels when it’s necessary. Plus, some increase the torque to get out of rugged terrains such as mud, deep water, sand, and snow. 

Vehicles that have 4WD also come with a transfer case. Instead of standard transmissions, a transfer case has two sets of gears: high-range and low-range. Pushing a button, twisting a knob, or pulling on a lever, drivers can select between these two modes. 

High-range gearing uses standard gear ratios. This means that they deliver the best power and torque for city and highway driving. Usually, the difference in size between gears isn’t that drastic. 

Low-range gearing uses specialized gear ratios. The difference in size between gears is higher, so a smaller pinion moves a bigger one to generate more torque. This translates to slower but more powerful driving. 

Also, as its name specifies, a 4WD system powers all four wheels when needed. Because the engine is sending power to all four wheels instead of two, the vehicle might feel slower. Fuel consumption might also increase. 

The benefit is that all four wheels are turning with increased torque. Therefore, they can grip the terrain better. But, there’s a risk to this operation. 

When the front wheels turn, one must do so at a slower pace than the other. When the front differential is locked, both wheels turn at the same speed (as in 4H and 4L situations). In cases with less grip, this is fine because the wheels are looking for grip. 

But, in asphalt, if you turn with 4H or 4L engaged, the wheels might force the differential to rotate at a more aggressive pace than it needs to, damaging it. It’s essential to understand when to use each mode, which we’ll explain in the following section. 

When To Use 2H, 4H, Automatic 4H, and 4L

2H

2H, also known as two-wheel drive, is the standard driving mode in most GMC Sierras. Some come with permanent 4WD, and we are going to detail which in another section. 

In this setting, the transmission is powering the rear wheels. The transfer case is in high range and hasn’t engaged the front differential. 

If you’re driving on asphalt and there’s no loss of traction, then you should use 2H. In this mode, there’s no risk of damaging 4WD components. 

4H

4H stands for High-Range Four-Wheel-Drive. This setting is best for slippery or loose surfaces. Think of gravel, ice, and sand. 

In this setting, the transfer case engages both the front and rear axle. Both differentials are turning and at the same speed. Since all four wheels have power, the vehicle can handle more challenging terrain easily. 

But also, since all four wheels are turning equally, you shouldn’t use this mode on surfaces with good traction. This mode places additional stress on the front axle, transfer case, and transmission, leading to damage.

As soon as road conditions improve, you should go back to 2H. 

Automatic 4H

GMC’s Automatic 4H is a system that engages the front axle when it senses that there’s less traction. This feature is only available in some vehicles that come with electronic transfer cases. It’s ideal for situations that you will have good and bad traction. 

GMC states that there’s no risk of using the Automatic 4 HI system on any road condition. But, you might be adding unnecessary wear to 4WD components. 

4L

4L stands for Low-Range Four-Wheel-Drive. It refers to the setting with the highest torque available. All four wheels are turning at the same speed, and the transfer case has selected the largest gears to ensure the most grip. 

This setting is ideal for deep mud or snow, heavy sand, and water. Because of the additional torque, drivers can have more control. In fact, this setting also provides engine braking. This is essential for controlled descents in steep hills with less traction. 

GMC states that there are several precautions with this mode. First, to engage it, you must stop the car and shift into neutral. Once there, you select 4L, and only then can you go into first gear. Do not exceed 45 mph when using this model. 

With this setting, especially, you must not drive on dry surfaces or roads with good traction. Doing so could lead to severe damage to your vehicle. 

You might not feel qualified to operate these modes. So, always be sure to check out the owner’s manual for a step-by-step process on how to use the GMC Sierra 4WD system. Now that we’ve covered each setting let’s talk about which GMC Sierras come with 4WD. 

Which GMC Sierras Have 4WD?

The GMC Sierra 1500 comes in five trim lines. Each of them has particular options and extras. The following table explains which of these comes with 4WD. 

Model2WD4WD as optional4WD as Standard
SLEYesYesNo
ElevationYesYesNo
SLTYesYesNo
AT4NoNoYes
DenaliYesNoNo

GMC offers an optional 4WD on its three most basic trim levels, the SLE, Elevation, and SLT. These are options for those looking for a luxury truck that works hard from time to time. 

The AT4, on the other hand, is an all-out offroading trim level. IT only comes with 4WD and other extras to make it more capable in the most challenging terrain. 

The top-of-the-line Denali is the opposite. This Sierra doesn’t come with 4WD, not even as an option. It’s designed for urban driving and occasional towing as well. 

The GMC Sierra Heavy Duty, known as the 2500/3500, comes with 4WD as optional in all its trim levels, including the Denali. Only the AT4 comes with no option for 2WD.

It’s worth noting that you might find an upwards arrow representing High and a downwards arrow representing Low. 

GMC Sierra 4WD Roundup

This article aimed to answer how to use the 4×4 on a GMC Sierra. This truck can shift from 2H to 4H on the move, as you only need to turn on a knob to engage the front axle. But, to use the 4L setting, you need to come to a complete stop.

Once you’ve fully stopped, you have to shift into neutral, and only then can you engage the 4L. The same process applies when you want to go from 4L to 4H or 2H. 

It’s important to remember that these settings require you to drive in conditions with limited traction. You should always use 2H when on asphalt and with good traction. Doing so will ensure that you don’t damage your truck’s components. 

If you find yourself in a condition where you alternate between good and bad traction, you can use the Automatic 4H. You could drive this in any situation, but it might lead to unnecessary wear on specific components. 

As you can see, operating the 4×4 on the GMC Sierra is easy. All you need to do is follow the steps on the user manual, and you’ll be traversing challenging terrain in no time. 

Kern Campbell

I've had a passion for four-wheel-drive vehicles since I was a kid riding in the back seat of my Grandfather's Jeep Grand Wagoneer. I have owned a lot of vehicles over the years. They each have their pros and cons and I look forward to sharing my knowledge with you so you can find the vehicle that's just right for your needs.

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