How to Shift an 18-Speed Transmission

by Ginger Kelly
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Semi image by Andrew Breeden from

Oversized semitrailers are typically outfitted with a manual 18-speed transmission. If you are inexperienced with a manual transmission, learning how to drive an 18-speed will be extremely challenging. If you are familiar with driving a manual transmission, you will probably find an 18-speed transmission to be a bit different, but still relatively simple in concept. You can still downshift and skip gears during acceleration if you are experienced and comfortable with the procedure, and if driving conditions permit. The 18-speed shift sequence may vary slightly from truck to truck, but the shifting process itself is generally the same.

Step 1

Set your vehicle's parking brake if it is not already engaged. Your parking brake will prevent the truck from rolling while it is in neutral. Some truck drivers prefer to park their vehicle engaged in first gear as an extra measure of precaution. Once you have set the parking brake, make sure that the truck is placed in neutral, meaning that the gear shift is not engaged in any gears.

Step 2

Depress the clutch pedal completely on the left hand side of the floorboard and start the engine. It is important to press the clutch until it is touching the floor and keep it depressed until the engine is fully started. Once the engine has started, you can release the clutch pedal while the engine runs and builds pressure for a few minutes.

Step 3

Depress the clutch again, and move the splitter selector to low while you shift into first gear. The splitter selector will be located on the top or side of the gear shift lever. It allows you to control which level of gears you are selecting to shift.

Step 4

Release the parking brake while putting your foot on the brake pedal. When you are ready, slowly allow the clutch to come up off the floor of the truck while you apply the gas pedal. Allow a full release of the clutch. This should be done smoothly and gradually while applying the throttle to ensure a smooth acceleration without any jolting or engine stalling. Depress the clutch again while shifting into the next gear. You will continue to accelerate as driving conditions permit with each subsequent gear shift.

Step 5

Change the range of gears by pressing the range-change button while depressing the clutch. The range-change button is usually located on or near the gear shift. For most vehicles, you will need to change the gear range before you are able to shift into the eleventh gear.

Step 6

Continue shifting gears in sequential order until you have achieved your desired speed for your road conditions. Always remember to depress the clutch pedal for each shift change before you place the gear lever into the desired gear. This will help avoid damaging the transmission while driving.

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