This section explains how to safely manage inclines and declines by choosing the correct gear, using differentials properly, and applying engine and air brakes in a controlled way. You learn how to prevent over‑acceleration, overheating, and traction loss through a steady, low‑and‑slow approach.
Driving safely on hills requires discipline, anticipation, and a clear understanding of how your vehicle responds to increased load and changing momentum. Uphill and downhill routes place added stress on your engine, brakes, and driveline components, and they demand heightened awareness from you. Your goal is to manage inclines and declines with steady control, thoughtful decisions, and consistent awareness of your surroundings.
Before beginning an uphill climb, make your most important decision: Engage the interlock differential selecting the correct gear. You need a gear that prevents over‑acceleration and avoids over‑revving. If the gear is too high, the engine may lug; if it is too low, the engine may exceed its intended RPM range. Both conditions increase mechanical strain and can cause loss of momentum. Choose a gear that provides steady power at a controlled RPM so your vehicle can pull the hill without unnecessary stress. Ask yourself, “Do I have enough torque in this gear to maintain a stable speed up this grade?” If you are unsure, shift before you begin the ascent.
As the grade steepens, think about traction and weight distribution. If your vehicle is equipped with a differential lock, engage it as designed to help maintain stability and reduce wheel slippage. Use it only after engaging interlock differential. Back axle preferably before traction is lost and never at higher speeds. If the Truck has differential lock on both axles it can make steering difficult as it will make the vehicle push straight and not want to turn.The goal is not added power but controlled, consistent movement up the hill.
Descending a hill requires the same level of intention. Select a lower gear before you begin your descent so the engine can help control your speed. Relying too much on air or service brakes can cause them to overheat and lose effectiveness when you need them most. Engine braking provides predictable speed control without constant pedal pressure. If your speed begins to rise, apply gentle, modulated braking long enough to return to a safe range, then release the brakes to allow them to cool. This method protects brake performance and prevents sudden or excessive deceleration. The Rule has always been 1 gear lower than what you pulled the hill in, for example you pull the hill in 7th gear you descend the hill in 6th gear.
As you continue downhill, stay alert to how the vehicle feels and how it reacts to small adjustments. Momentum increases quickly on a grade, and once speed begins to run away from you, it can be difficult to regain control. Avoid abrupt braking, stab braking is absolutely not to be done on slick roads.Also avoid unnecessary gear changes, or any attempt to accelerate downhill. These actions disrupt the balance you have established. Instead, focus on smooth, intentional inputs that keep your vehicle steady and predictable.
Whether climbing or descending, the guiding principle is the same: low and slow. This approach is not simply about caution—it is about mechanical control, traction management, and preventing avoidable failures. By managing momentum to a subtle transition to torque, preventing spinout slowing down, improving stability, and creating safety margins that help you respond to unexpected hazards such as sharp curves, weather changes, or stopped traffic.
When you consistently select the right gear, use the differential appropriately, and modulate your engine and air brakes with intention, you build confidence on steep terrain. These techniques, combined with steady situational awareness, allow you to maintain predictable control in challenging conditions. In hill driving, excellence is not about speed; it is about precision, preparation, and respecting the forces acting on your vehicle. Remember: low and slow is the rule. Caution engaging interlock differentials should never be done if wheels are spinning this will seriously damage your vehicle differentials. I have always removed my foot from the throttle and at a 30 mph engaging interlock differential without damage to my vehicle this maintains momentum and easy transition to torque. Torque is where you pull with power directly to the ground. Sadly, many truck schools don’t teach how to use them. Caution use of the engine brake is 1 of the internal forces that can disrupt motion. They are to be used from moderate to low positions; too much torque can cause the wheels to spin backwards. This is why we use engine brakes disengaged downhill with snowchains. One of this industry failure is teach how to use Snowchains and it puts the public at risk as well as the driver the common twisted link soft steel snowchain is not recommended for OTR use, as the authors opinion it costs more than there worth and discourages the professional driver not to use them as they will not hold up on black top or concrete road surfaces. Damages equipment and the driver is to blame. Snowchain should be used when there is enough snow or ice to keep them from being in contact with the road surface. But all too often chain control requires the driver to install them before the snow line due to volume of traffic. This is why I use only the best tool made. Driving in adverse weather conditions, in my opinion, is an opportunity to shine.