4WD High (4H)

4WD High (4H) is an essential feature on dedicated 4x4 off-roaders. Simply put, it is the four-wheel-drive mode deployed when a vehicle needs to navigate challenging surfaces (such as snow, mud, or sand) at higher speeds.

⚙️ How Does It Differ from Standard 4WD?

• Mechanical "Rigid Connection": Unlike the on-demand AWD systems found in urban SUVs, 4WD High (4H) uses a transfer case to mechanically lock the front and rear axles together, typically delivering a fixed 50:50 torque split. Consequently, it must not be used on dry tarmac (such as highways and city streets), as it cannot accommodate the rotational speed difference between wheels when cornering, risking driveline binding, transmission damage, and even vehicle rollover.

• Division of Roles with 4WD Low (4L):

  • 4WD High (4H): Featuring a direct gear ratio in the transfer case, it allows the vehicle to carry momentum at higher speeds (generally recommended below 80 km/h), making it ideal for snow, mud, sand, and gravel tracks where maintaining speed is crucial for clearing obstacles.

  • 4WD Low (4L): Featuring a deep reduction gear ratio, it multiplies wheel torque by 2 to 4 times. It trades speed for immense tractive effort, engineered specifically for extreme self-recovery, steep hill climbs, and rock crawling, where crawl speeds are minimal but wheel torque is immense.

When tackling snow, muddy stretches, or soft sand, engaging 4WD High (4H) provides optimal traction while preventing the wheelspin that leads to getting bogged down from excessive torque. Inadvertently selecting 4WD Low (4L) in these scenarios may deliver too much wheel torque, digging the tyres into loose ground and sinking the vehicle further.

🚗 Practical Tips

• A Unique Exception: Super Select 4WD: The Super Select 4WD system featured on models like the Mitsubishi Pajero is a notable exception. Its 4H mode incorporates a centre differential, allowing full-time four-wheel drive at high speeds even on dry tarmac, delivering enhanced on-road stability that conventional part-time 4WD setups cannot match.

• When to Shift: Engaging 4WD High (4H) traditionally requires bringing the vehicle to a complete stop or rolling at minimal speed (e.g. below 8 km/h). However, requirements vary by model; for instance, the part-time 4WD on the Prado and Mitsubishi's Super Select 4WD support "shift-on-the-fly" at speeds of up to 100 km/h. Always consult your vehicle's owner's manual for specific operating procedures.