Driving in 4-Wheel Drive on Dry Pavement (RISKY)
Driving in 4H on dry pavement with a part-time 4WD or with a permanent 4WD in 4H-L (center diff locked) is not recommended since it can cause drivetrain binding, premature tire ware and wheel hop if driven for extended periods on high-traction surfaces.
So what happens to your drivetrain when you engage 4WD or 4H on dry pavement, or you forget to disengage 4H after you leave the dirt roads? How long will it take for binding to occur?
It happens to the best of us and even after 20+ years of experience and owning a variety of 4x4s I’ve on occasion forgotten to remove my 4×4 from 4H when I hit the tarmac. Fortunately, my experience has never ended badly, however, if driven in 4H for extended periods it could result in catastrophic damage to your 4WDs drivetrain system.
The next part of this article will go into more detail about the cause and effects of Drivetrain binding and later how the viscous coupling of a permanent 4-wheel drive functions.
Driving in 4-Wheel Drive on Dry Pavement (4H)
Dry pavement is a surface that is very “grippy”, which is ideal for 2-wheel drives in the form of front and rear-wheel propelled vehicles. The concrete compound is even designed to deliver sufficient grip in wet and snowy conditions. This is possible since the concrete surface is not 100 percent smooth but rather coarse and porous, allowing soft compound tires to grip for reasonable levels of traction, even on rainy days.
4×4 Tires vs Highway Tarmac
- The ironic fact about 4WD is that it requires slight wheel slippage for it to return good traction. So, it needs to be able to slip to prevent it from slipping…
- Potential damage includes issues with u-joints, yoke failure, driveshaft twisting, and transmission gear damage
- Concrete pavements on the other hand are designed for optimal grip which is incompatible with 4WD’s and the need for wheel slippage when 4H or 4H-L is engaged.
Most 4WD are equipped with AT (All-Terrain) tires. The type of Rubber compound used in AT tires is designed to grip well on a variety of surfaces, including highway tarmac and dry concrete even when wet. That’s bad news for your 4WD when neither one wants to concede.
So armed with the above information, it’s reasonable to conclude that a locked center differential (4H) of a part-time 4-wheel drive and a high traction dry pavement or highway are not a good combination.
Next, let’s look at the effects of driving on the highway in 4WD.
Driving in 4-Wheel Drive on Highway
When driving on the highway, your part-time four-wheel drive should always be in 2H. This means the front driveshaft is disengaged and the front wheels are simply coasting along. Great! No risk of drivetrain binding there. In 2H mode, all the power is exclusively sent to the rear axle via the rear driveshaft. The transfer box of a part-time 4WD is also not engaged in 2H mode.
When is it Safe to Drive in a 4-Wheel Drive on the Highway?
In certain low-traction conditions like snow-covered or icy roads, using 4-wheel drive on pavement or highways might be considered by the driver. Engaging 4H depends solely on the driver’s judgment, ensuring the surface is sufficiently slippery to prevent drivetrain binding. Unlike AWD or permanent 4WD with viscous couplings allowing varied speeds between front and rear driveshafts, part-time 4WD lacks this feature.
4-Wheel Drive Drivetrain Binding
So let me tell you a quick story.
So the exact phenomenon occurred to me when I purchased my first 4-wheel drive. It was one of the most exciting moments of my life. I couldn’t wait to test out my vehicle’s 4-wheel drive system and headed off to the nearest forest track in my area. Everything went fine and I was so impressed with the capabilities of my new 4-wheeler.
I tested every single function on the super-select gearbox, and boy does it have options. There’s a gearbox selection for every driving scenario, it was such an amazing design. You could even engage the rear diff-locker when the 4H was engaged. How cool is that!
Anyway, I tested it off-road and did my thing, after which I headed back home, driving on the tarmac highway.
Everything was going fine, however, I happened to notice the vehicle handling was slightly “tauter”, more “compressed” than before. After taking a few turns, I thought I heard some weird noises emanating from my rear tires. It had chunky BF ATs fitted. I slowed down a bit and poked my head out the window to try and see what was up, only to realize, I’d been driving in 4H on the highway. Now this being my first 4WD and me being caught up in the 4×4 hype, I forgot to disengage the 4H mode.
I immediately stopped the vehicle, jumped out, and had a look around. I checked to see if I’d damaged any drivetrain components or my tires. Everything seemed fine. I disengaged and put it in 2H mode and proceeded to drive off at a very slow speed. The vehicle felt fine, it just felt slightly “tighter” when I drove in 4H. After having read in my owner’s manual, it was then I realized the Mitsubishi super-select box allows for 4H driving under most conditions, and it shouldn’t cause any damage, even when driving on the highway. What a relief! Had it been any other vehicle, I could have caused some serious damage.
Don’t let this happen to you! Remember to disengage 4H when you leave the dirt roads and head back onto the highway.
Permanent 4WD vs AWD on Dry Pavement
So we know a permanent 4WD and an AWD can safely drive on dry pavement since they have a special component called a viscous coupling or a multi-plate clutch system. These clever designs allow for varied rotational speeds between front and rear driveshafts, allowing them to drive on a variety of road surfaces.
The main difference between the AWD and a permanent 4WD is the following:
| AWD Sedan Characteristics | Description |
|---|---|
| No engagement for the center differential | Center differential in AWD cannot be engaged or left open |
| Lack of low range in the transfer box | A center differential in AWD cannot be engaged or left open |
| Limited ability to switch off traction control | Inability to fully deactivate traction control systems off-road |
| AWD with electrical multi-plate clutch system | Utilizes electronics and wheel sensors to manage all four wheels |
| These systems are often unable to be disabled in most cases |
A permanent 4-wheel drive, on the other hand, is a more basic design with rugged off-road capabilities. It has low-range gearing and in most cases diff lockers in the rear axles for challenging off-road driving. When driving under normal conditions like a highway or dry pavements the center diff is left open.
Both AWD and permanent 4WD can safely be driven on Dry pavement without risking damage.
Can You Back Up In 4WD On Dry Pavements?
When you have a part-time 4WD you need to be aware of the dangers and risks of engaging 4H anywhere other than when driving off-road. So the rules apply the same when backing up in 4WD. You want to avoid backing up or reversing in 4WD on pavement if the ground surface is dry and traction is good.
You will experience strain, in the sense that, the vehicle will feel very constricted and hesitate to turn. Steering will feel very taut and understeer will be obvious. You’ll hear tires screeching as they lose grip on the pavement due to the drivetrain’s inability to compensate for the differences in rotational speeds between front and rear driveshafts. These are all signs that the driving surface is not slippery enough and that you probably should disengage 4H.
Final Thoughts
Get to know the behavior of your 4WD so you can quickly identify if anything feels out of the ordinary with its handling and steering.
We’ve also established that 4WD mode should be engaged when driving conditions are bad and surface traction is low. These include muddy trails, icy roads, snow roads, sand, and dirt roads. All other driving on highways and concrete surfaces is best done in 2H.
