If you’re reading this, you most likely drive a 4WD and have concerns about the potential damage you could be causing by leaving your truck in 4 Wheel Drive, perhaps parked in 4H overnight, or driving in 4H for extended periods at a time. It is important to be aware of the potential damage you could cause if you do not operate your vehicle within the operating specification as set out by the manufacturer in the owner’s manual. Yeah right, nobody reads that thing… Therefore unintentional misuse or abuse could cause extensive and expensive damage to your 4WD. This article will discuss the risks of operating your 4WD in a specific setting or 4WD modes for extended periods.
There is low to no risk of mechanical damage by parking your vehicle in 4 wheel drive mode overnight. Leaving your truck in 4WD mode when surface traction is limited, such as snow, sand, or ice, could be advantageous as it decreases the potential of the vehicle losing traction. Parking in 4 Wheel drive mode on a slippery surface overnight keeps the vehicle stationary by utilizing the drive-train to assist the parking brake.
There is, however, much more to know about the correct operation of a 4WD. Many 4WD and off-road vehicles have different drive-train setups and not all 4×4 systems are created equal. What are the consequences of driving your vehicle in 4 wheel drive when you should not have? I will briefly discuss the basic differences between AWD and 4WD. If you would like to know more about this subject, continue reading…
Can You Leave Your Truck In Four Wheel Drive?
A good rule of thumb is, if you are parked facing a downhill slope or decline, park it in reverse gear. If you are parked facing uphill, leave it in 1st gear. Always park the vehicle in the opposite gear your vehicle is facing. There is always the possibility of your parking brake failing or losing tension over time, especially if you are parked on an incline or a decline for extended periods. The transmission and transfer case would essentially keep the vehicle firmly locked in place and safe from rolling down a driveway, possibly running into something or someone causing major damage to your vehicle and somebody else’s property.
When the vehicle is parked in 4WD, the drive-train will be “locked” in gear, 1st or reverse gear. There is also less wear and tear on your parking brake. It is very important to ensure you remove the transmission out of 4 wheel drive before you pull-off in the morning, especially if it is not a permanent 4 wheel drive vehicle and the driving surface is not slippery i.e snow/ice/sand, as this will cause substantial tire wear, high fuel consumption and transmission drive-train wind-up. Perhaps have a read on how 4WD affects gas mileage here.
Is It Ok To Drive In 4 Wheel Drive All The Time?
So in order to get the correct answer for your vehicle application, we need to understand one important fact and that is, there are essentially two types of 4×4’s.
- A full-time 4WD which is essentially a permanent 4 wheel drive
- A part-time 4 wheel drive. Non-permanent 4×4
So what is the difference and how does it affect the operation of the vehicle?
Unless traction is bad, It is not advised to drive in 4WD mode for extended periods of time with a non-permanent 4×4 as this will result in “axle binding”, also known as ”drive-line binding” or “drive-line wind up”. Extended driving in 4-Hi, with a part-time 4WD truck, on a high traction surface like pavement, will result in drive-train components like u-joints, axle, transfer gears, bearings, and drive-shafts getting damaged and eventually failing.
Permanent 4 wheel drive
Permanent 4 wheel drive means the vehicle cannot be removed or taken out of 4×4 (4H)mode at all. This means the vehicle is always in 4WD mode and there is no risk of operating and driving it on ANY particular surface in this mode. Permanent 4WD makes use of a drive-train component (viscous coupling) that allows the drive-shafts to operate independently without causing any drive-line wind-up.
NB: if your 4WD has the ability to lock its center differential, always ensure that it is disengaged or unlocked before you venture back on to the tarmac or any hi-traction surface.
What is transmission wind-up?
Transmission wind-up occurs when a part-time 4WD vehicle is operated on a non-slippery surface like tarmac or pavement which does not allow the left and right side wheels on the axles to turn at different speeds while taking a bend.
When cornering in 4WD, the difference in rotational speeds between the two inner wheels and 2 outer wheels causes the axle drive-train to wind up, resulting in major damage to tires and other drive-train components. The high torque generated inside the transfer box and other drive-train components are susceptible to major damage when the transmission is placed in four-wheel drive and made to turn corners on high-traction surfaces.
For example: If you are turning left the two wheels on the left side of the axles are turning slower than the two on the right side because the circumference is smaller. If the vehicle is in 4WD mode on a high traction surface then drive-train wind-up occurs because the axles want to turn at the same speed and that stress which it generates on the drive-train is what causes the axle-binding.
Transmission wind–up can be identified by tight gear shifting, grinding, transmission stuck in a gear, difficulty turning, wheel hop, combined with increased fuel consumption. These are some of the immediate tell-tale signs you have transmission wind-up as a result of driving in 4WD on a non-slippery surface. More about this later.
So why are all 4×4’s simply built with permanent 4WD then?
Well, there is a trade-off to having the capability of being able to operate and drive on any surface with no risk of damage to tires and drive-train. The trade-off for permanent 4WD is the following:
- Slightly Higher fuel consumption than 2WD vehicles
- More operational components (more serviceable parts)
- Higher maintenance costs
- High repair costs
- More expensive purchase price (more components and technology built-in)
- Heavier vehicle curb weight
- Usually has a lower Towing Capacity than a 4×2 version of the same make and model
So it is not all roses with permanent 4WD vehicles even though they have a huge driving and safety advantage over two-wheel drives on slippery surfaces like snow, ice and dirt roads. Permanent 4WD vehicles and AWD’s offers superior cornering abilities since the front wheels are pulling while the rear wheels are pushing simultaneously, at varying speeds during cornering, thus providing a more sure-footed feel and superior grip and traction on a variety of surfaces.
Below are some examples of vehicles with permanent 4WD and AWD
- Subaru Outback
- Toyota Fortuna 4×4
- Audi Q5 Quatro
- Toyota 4Runner
- Jeep Grand Cherokee
- Land Rover Discovery
- Honda CRV AWD
Difference between 4WD and AWD facts
- Full-time 4WD works well on-road and is very capable off-road too.
- Roughly 25% of the vehicle’s torque is distributed to each wheel.
- Certain manufacturers split the torque distribution 50/50 while many prefer 60/40
- Other manufacturers opt for an 80/20 torque split for a sportier feel. With the higher percentage of torque always being distributed to the rear axle.
- Full time 4 wheel drives usually have a centre diff that can be locked
- AWD does not have a lockable centre diff
- AWD has no low range gearing
- AWD has no transfer case
- AWD has no axle lockers
The significant difference between the two types is that a 4 wheel drive has a low-range transfer case whereas an AWD does not have any low-range capabilities, transfer case, or diff lockers.
This is not always the case anymore with the advancement in technology the lines are becoming more blurred with modern vehicles. You now have vehicles like the VW Amarok 2.0 and V6 auto that is a permanent 4WD but does not have a low range transfer case and cannot lock the center differential. It makes use of a crawler gear, advanced traction control, and some clever German electronic trickery to achieve what a traditional 4WD with low-range can and more. So it’s like a hybrid AWD and 4WD. Brilliant engineering!
Part-time 4 wheel drive
Part-time 4 wheel drive or 4×4 means the vehicle can be operated in 2-wheel drive mode as well as 4 wheel drive mode as you wish. These modes can be selected with a short gear stick in the older 4×4’s or the more modern Utes and trucks make use of an electronic 4×4 button option.
Most vehicles with part-time 4WD modes have a low range transfer case making it very capable off-road, much more so than AWD vehicles. A part-time 4WD vehicles are propelled by the rear wheels in 2H mode, usually on the tarmac and other high traction surfaces. This allows the vehicle to deliver decent fuel economy on-road while having the ability to offer excellent off-road capabilities in 4H and 4Lo when needed. It is a good mix with the best of both worlds.
When is it not good to engage 4 wheel drive?
So by now, you should know that if the vehicle has the option of engaging 4-Lo or locking the center diff in 4H mode then you are not driving an AWD vehicle but rather a 4WD. Traditionally, it should have a transfer case with low-range functionality. With a non-permanent 4WD configuration you need to exercise more caution and be informed of the Do’s and Don’ts of driving it in 4WD mode.
4WD vehicles should NOT be driven in 4H for extended periods when the surface is not slippery, like on a dry highway. Surfaces like tarmac, pavements, and bitumen should be avoided in 4WD mode when you have a part-time 4WD as this will cause significant damage to both drive-train components, transfer case and tires, not to mention your bank account.
Below are some examples of non-permanent 4WD vehicles:
- Toyota Tacoma
- Toyota Hilux
- VW Amarok Manual (Stick shift)
- Ford Ranger Ute (Stick shift)
- Isuzu DMAX (Stick shift)
In Conclusion
So the take-home here is, you need to familiarize yourself with the owners and operations manual of your specific vehicle before attempting any 4 wheel-drive. However, parking a vehicle in 4 wheel drive or 4H is quite safe even if it is permanent or non-permanent 4 wheel drive. DO NOT drive a non-permanent 4 Wheel drive on surfaces with sufficient grips like bitumen/tarmac, cement, and pavements. Surfaces like grass, asphalt, sand, mud, and snow are perfectly suited for non-permanent 4 Wheel drives.
Parking in 4WD overnight and in a gear will allow the transmission and drive-train to assist in holding the vehicle securely in a stationary position. Do not rely solely on the drive-train to keep the vehicle stationary when parking and always set the parking brake first.
Happy 4-Wheeling and remember, safety first!!!