How Fast Can You Safely Drive In 4H: The eye-opening truth you need to know + Forum Opinions
Driving over 55MPH in 4H on a low-traction surface is not recommended. Similarly, 4WD-Lo should not exceed 10mph. If safe, switch to 4WD-High when driving faster than 10mph in 4WD-Lo.
With over 20 years of off-road and overland experience, I’ve learned the importance of looking at all the contributing factors. What do I mean by that? For example, what exactly is happening to the drivetrain of my 4WD when I engage 4H? Also, is driving fast in 4WD always a good idea?
Remember, when you engage 4WD (4H) you should always be on a low traction surface. This is very important and something I am always aware of since there is always the risk of drivetrain “binding” if I choose to ignore this rule.
With that being said, I am aware that a low-traction surface could be a dirt road, sand, grass, a muddy track, a wet road, or a slippery snowy, or icey highway. These are what I consider to be perfect driving conditions for 4H. Driving 55MPH in 4H and below is perfectly safe under most of the above-mentioned conditions.
There will, however, be certain road surfaces and environments, such as wide, long dirt roads that you might feel comfortable driving over 55mph. I would always exercise caution since there are external factors that are outside our control that we need to consider.
Examples of hazardous conditions:
Hazardous Conditions |
---|
Wild animals running in front of the vehicle |
Tire burst |
Sudden bends in the road |
Uneven road surfaces |
Deep holes camouflaged by debris |
When driving over 55MPH in 4H on these low traction surfaces with the above-mentioned risks, you do well to ask yourself, “Will I have enough time to react and stop the vehicle in case of emergency? Will I have enough time to reduce my speed enough to avoid any possible obstacles or collisions?
Let’s now look at what driving surfaces warrant engaging 4WD-4H.
Where Should You Drive in 4H
When we venture outdoors on our 4WD trips, we need to drive long distances on city highways before we even reach the beginning of our offroad adventure. If, like me, you are driving a part-time 4WD then you will, of course, be in 2H mode when driving on a tarmac or cement driving surface with good traction. This is important to prevent drive-train binding.
When I reach the dirt roads and off-road mountain tracks I immediately engage 4H. Unless you drive a permanent 4WD, then you simply proceed as normal since you already are in 4H all the time. Alternatively, if your vehicle is equipped with a 4WD system that has 4H-Auto then this would be a good time to engage 4A.
- When your vehicle is in High-range 4H, the engine torque is sent to both the front and rear axles.
- The torque is, in turn, split 50/50 between each wheel on that axle, which means each wheel receives 25% of the engine’s total power.
- This makes the vehicle handle more stable and grip a lot better since more traction is gained by all 4 wheels propelling the vehicle forward.
Examples of low-traction surfaces include:
Driving Conditions | Descriptions |
---|---|
Slippery icy roads | Roads are covered with snow, potentially reducing visibility and traction. |
Snowy conditions | Roads covered with snow, potentially reducing visibility and traction. |
Sand tracks | Roads commonly found in rural areas are often unpaved and uneven. |
Muddy tracks | Roads are covered with snow, potentially reducing visibility and traction. |
Farm roads | Tracks consisting of loose sand, are common in deserts or coastal areas. |
Wet rocky surfaces | Roads covered with grass, are sometimes uneven and challenging to navigate. |
Grassy surfaces | Tracks or trails with wet, soft soil, make the surface muddy and slippery. |
How Driving Fast in 4H Affects Braking
When driving on a slippery low traction surface, the braking distance on a vehicle is drastically increased. This means you need to seriously adjust your driving style to compensate for the extended stopping time.
The stopping distance on a low traction surface can increase by as much as double (2x) that of regular braking distances, such as when driving on a tarmac surface.
The 3 key elements that make up the braking distance are the following:
- Traction
- Reaction time
- Stopping time
So when driving on a low traction surface such as wet roads, dirt, ice, or snow your reaction time combined with the stopping time is increased by ten. If that’s not a sobering fact, then I don’t know what is!
How Driving Fast in 4H Affects Cornering
When cornering on a low traction surface we need to consider the dynamic of the vehicle and the changes it undergoes in these conditions. Elements like cornering, braking, and acceleration are all negatively affected and we need to be aware of and prepared for that.
- When cornering in 4WD on a slippery surface we want to avoid sudden braking and aggressive cornering.
- The vehicle can easily lose traction and veer off the road, resulting in an accident.
- Practice progressive braking where you gradually apply lighter pressure from further back to slow the vehicle down before the bend.
- Avoid braking in the bend is also a key factor since the weight will be shifted and traction is lost more easily.
Keep the steering motion smooth and controlled and avoid sudden jerky motions.
How Driving Fast in 4H Affects the Handling
If you are driving fast on a low traction surface the handling of a 4WD or any vehicle is drastically reduced. The steering is no longer crisp and direct. If you feel the vehicle not responding well while turning, In most cases it means traction is low, hence the understeering effect.
A 4WD can easily drift in a corner when surface traction is low, and if the 4WD is not in responsible hands, an accident is likely to happen.
Again, avoid sudden jerky motions on slippery roads since this will negatively affect handling. Progressive braking combined with slower turning and easier throttle pressure are all safer driving practices.
The Function of 4WD Low-Range
The “Lo” on 4-Lo represents the low-range gearing that has been engaged. This means the ratios of the gearbox combined with the transfer case are extremely reduced and only designed to be used in extreme driving conditions.
- Most off-road 4×4 vehicles have a 2H, 4H, and 4-Lo setting.
- When 4-Lo is engaged it means the 4WD power and torque are more readily available in the sense that, the revs will almost always be in the powerband.
- Stalling the 4×4 is less likely and many modern 4WDs are even equipped with an anti-stall device.
When in 4-Lo mode the 4WD can more easily drive on challenging terrain without placing undue strain on the transmission/gearbox, clutch, Transfer Case, and engine.
Challenging terrain could be:
- Loose deep beach sand
- Thick mud
- Rock crawling
- Steep uneven low-traction Inclines
- Long technical declines
- Deep River crossings.
The function of 4-Lo is to provide maximum power and traction under very challenging driving conditions. This is designed to be used when driving conditions are so challenging that you cannot drive over 10MPH.
If you are doing any sort of rock crawling where you are required to negotiate each obstacle precisely and choose a driving line, will be an ideal time to engage 4-Lo.
Driving through thick loose beach sand with a load will require 4-Lo to prevent damage to your vehicle’s clutch or to decrease the risk of overheating the gearbox if you are driving an automatic 4WD vehicle.
Real-World REDDIT Forum Experiences
You shouldn’t shift in/out of 4H over 45mph. There is no maximum speed, it’s safe as conditions and common sense dictate. 4LO max speed is 25mph. With chains, max speed is 30mph regardless if you are in 4wd or 2wd.
If you need 4WD to drive at 70mph, you’re either driving recklessly or need better tires. Living in the mountains you should have snow rated, if not studded tires. M/Ts will not cut it.
https://www.reddit.com/r/JeepGladiator/comments/sesg5l/4h_driving_can_i_drive_highway_speeds_in_4h/
There’s no max speed for driving in 4Hi in a part-time 4wd system, but as mentioned you don’t want to try to shift INTO 4Hi above a certain speed as detailed in your Owners Manual.
https://www.toyota-4runner.org/5th-gen-t4rs/294382-trd-off-road-max-speed-4h.html
Helpful Resources
- https://www.reddit.com/r/JeepGladiator/comments/sesg5l/4h_driving_can_i_drive_highway_speeds_in_4h/
- https://www.toyota-4runner.org/5th-gen-t4rs/294382-trd-off-road-max-speed-4h.html
Final Thoughts
As a 4WD driver who drives challenging terrain, we should always know when to engage 4H and 4Lo. Knowing how fast to drive in 4WD is essential to preventing serious damage to your truck, your wallet, and your ego. Do not attempt to drive over 55-60mph when in 4WD mode irrespective of the driving conditions. Remember, the vehicle dynamics are very different on low traction surfaces so adjust your driving style.