The Four-wheel-drive system, popularly known as “four-by-four” (4×4), is an automotive feature that allows the engine to deliver power equally to the four wheels of a vehicle.
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This is found in vehicles designed for off-road conditions such as the Hummer. In this piece, we look at 4×4 in Hummers.
Are all Hummers 4×4?
All Hummer models, including the H1, H2, and H3 have 4×4 controls. However, the individual features present in the four-wheel-drive system varies across different models.
But first, let us discuss how four-wheel-drive systems work.
What is Four-Wheel Drive?
Often referred to as 4WD or 4×4, four-wheel drive is a drivetrain with two axles which allows all four wheels to get torque or power at the same time. It differs from the two-wheel-drive (2WD) system, where the drivetrain delivers power only to the two front tires.
Note: The drivetrain is the part of the vehicle responsible for transferring power from the engine to the wheels.
While 2WD is suitable for traveling on paved roads where there are little or no obstacles, it is unsuitable for off-road driving. For instance, a 2WD truck could get stuck while climbing a steep hill because the two wheels receiving power are spinning freely without contacting the ground, causing the vehicle to lose traction.
But if your vehicle has engaged 4WD and is stuck in the same position, the drivetrain will deliver power to the wheels contacting the road. This will spur movement and allow you to get out of the sticky situation.
The 4WD system of a vehicle may be part-time or full-time, depending on the make and model of the vehicle. With part-time 4WD, the truck operates in 2WD, but you can quickly switch to 4WD when the vehicle needs additional traction, particularly in an off-road condition. Full-time 4WD means that the vehicle is continually in 4WD mode all the time.
The Hummer is a full-time 4WD, which means you have to either stop the vehicle first and put it in ‘Neutral’ or park before engaging the various 4WD modes. On other occasions, you may have to drive at low speeds before switching.
The Hummer 4WD system has various modes, including 4-High, 4-High Locked, 4-Low Locked, and Neutral. These modes have different uses and specific conditions to be engaged for maximum efficiency.
When Should You Use 4-Wheel Drive?
The primary aim of the 4WD is to help the vehicle gain more grip on the surface, especially when there is low traction. A suitable time to put your vehicle in 4WD mode would be when the roads are slippery because of ice, and you are wading through deep mud or sand or climbing steep hills.
As soon as you discover your Hummer lacks enough traction and might slip or skid out of control, engage 4-Wheel Drive. However, it is necessary to decide which 4WD mode you want to use.
Below is a guide to engaging the various modes of the 4-wheel Drive System:
This 4WD model is similar in speed and transmission to 2WD. It allows for the front and rear axles to move at different speeds and should be used for normal street and highway driving situations.
This is an upgrade on the 4-High mode as it locks the front and rear axles to give the vehicle extra traction. The extra traction can help when the vehicle is traveling on slippery surfaces. 4-High Lock should be used when traveling on terrain covered in ice, shallow water, sand, snow, or mud.
The 4-Low Lock mode locks the front and rear axles together and shifts to a 2:64:1 gear reduction in the gear set. This shift reduces the speed of the vehicle while providing higher torque to the wheels. You can use this in the following situations:
- When you are climbing rocks or towing heavy items uphill.
- When you are descending steep inclines. It increases the effects of engine braking and prevents the vehicle from diving forward while descending.
4-Low Lock + Rear Differential Lock
This mode is only available when the transfercase is already in 4-Low Lock mode. This mode locks the rear axle shifts together, sending equal torque to both wheels. You should only use it when the vehicle needs maximum traction, such as when climbing large rocks or ascending steep hills.
You should use this only when the Hummer is being flat-towed behind another vehicle.
How Do I Put the Hummer in and out of 4WD?
Unlike newer 4×4 vehicles, the Hummer is a full-time 4WD, which means you have to park the vehicle or put it in Neutral before engaging and disengaging the various 4WD modes. Below are instructions on how to engage and disengage 4WD modes in your Hummer H2:
To put the Hummer H2 in 4-High mode, ensure that the vehicle is traveling at a speed lesser than 40mph then press and release the 4-High button on the transfercase mode selector.
For 4-High Lock mode, ensure the vehicle is traveling at less than 40mph, then press and release the 4-High Lock button.
To shift into this mode, ensure that the engine is running, and the vehicle is parked with the transmission in Neutral. After this, press and release the 4-Low Lock button.
To shift out of 4-Low Lock into 4-High or 4-High Lock, the engine must be running, the transmission in Neutral, and the vehicle parked. Then the desired mode should be selected before shifting into gear.
4-Low Lock + Rear Differential Lock
Before engaging this mode, ensure your Hummer is parked and already in 4-Lock Low mode, then press the Lock Rear Axle Button.
If you want to put the vehicle in Neutral, first ensure that you park the vehicle. After this, press the 4-High and 4-Low Lock button simultaneously for 10 seconds.
Note: The Hummer H2 is a full-time 4WD vehicle so you cannot turn off its 4WD controls. However, if you wish to use the vehicle for street driving, it is advisable to switch to 4-High as it is more similar to 2WD. If you want to tow the vehicle and don’t want the transmission shafts rotating, switch to Neutral Mode.
While the instructions above relate to the H2, other Hummers will probably use the same procedure. However, check your user manual to be sure.
Read our article which explains about Are Hummers a Good Buy Today?
What Are the Adverse Effects OF 4WD Use On Your Hummer?
While the 4WD system is useful, especially in off-road conditions, it has some adverse effects on the Hummer.
Wears the Engine
The addition of a transfercase to 4WD vehicles often means more weight and friction, especially as there are more moving parts. All these lead to more load on the engine.
To fully understand the effect of 4WD on the engine, consider this illustration:
Normally, power is transferred from the engine to the two front wheels to make the vehicle move. However, when 4WD is in use, only half the engine power goes to the drive wheels while the other half goes to the other tires.
To maintain its initial speed the engine will need to produce more energy than it did before since some of it is already being wasted on the other tires.
This will affect the performance of the engine and lead to more wear and tear.
Increases Fuel Consumption
Most 4WD vehicles are usually heavy because of the addition of extra components such as the transfercase and differentials.
This increased weight often means that the engine needs to generate more power to move the car. The extra burden increases fuel consumption and reduces your vehicle’s mpg rating.
Also, the engine requires higher torque to deliver equal power to the wheels simultaneously. This often translates into increased fuel consumption and engine wear.
How Much Off-road Terrain Can a Hummer Handle?
Because of its military heritage (the Hummer is based on the military Humvee), the Hummer can handle the most extreme of off-road terrains.
From its rugged body design, impressive ground clearance to its efficient 4WD system, the Hummer has all the qualities to handle the toughest environments with ease.
Whether you are racing in the desert, camping on a nearby mountain range or fording 3-feet deep streams, the Hummer is one of the most dependable 4×4 trucks in the world.
And it will take you safely to your destination in one piece.
In terms of off-road ability, the Hummer is arguably one of the best trucks in the world.
Compared to the Jeep, the Hummer has more ground clearance that allows it to scale obstacles on a straight line. However, it lacks the articulation of the Jeeps but will perform creditably in places with wide paths.
If you are looking for a suitable 4×4 vehicle to actualize your dream off-roading experience, the Hummer is the perfect truck for you.