Truck transmissions with more than 5 gears are common, due to the low gear ratios required to haul heavy loads. These heavy loads require more torque, but with more torque comes less speed. To reach highway speeds, auxiliary transmission gears were created. On an international truck, gears 1-5 are found in "low range." Gears 6 and 7 are found in "high range," controlled by a range switch on the gearshift knob.
Start the engine with the transmission in neutral, indicated by the loose "play" of the gearshift knob. Allow the engine to warm up and any air pressure systems to charge.
Depress the clutch and pull the gear shift all the way to the left and down. This is 1st gear. When you flick the range switch to "high," this position will be 6th gear.
Depress the clutch, push up, slightly right, and up to reach 2nd gear. Release the clutch. Note that shifting is done by the ear, listening as the engine reaches 80 - 90 percent of its RPM potential. Depress the clutch and pull straight back to reach 3rd, releasing the clutch once more. As you accelerate and approach the RPM red line, depress the clutch, push up, right, and down to reach 4th gear. Find 5th gear by pushing straight up from 4th position. At this point, you are at the far top right corner of the shift pattern.
Flick the range switch on the gearshift knob from low range to high range, depress the clutch, pull down, over to the far left, and down to reach 6th gear. Remember, this is the same position as 1st gear, but the "high range" has designated that it's 6th. Finally, find 7th gear by moving up, slightly right, and up.
Depress the clutch and move to the desired gear to down shift. Note the RPM range that each gear operates in. Each time you downshift, you'll want to ensure that the engine RPM is close to that gear's sweet spot to avoid over revving and unnecessary strain on the transmission components.
