How to Shift a Semi Tractor
The first thing a new driver notices when he tries to move a semi tractor is that it does not shift like a car. In a car, it is possible to shift gears at just about any rpm. However, if the engine in a truck is at the wrong rpm for the gear, it will only grind, no matter how hard he tries to force the gear shifter. Shifting a tractor-trailer smoothly takes practice, because not only do you shift up through the gears, you also need to shift down to assist the brakes in stopping the tractor-trailer. To shift a semi tractor, you should know how to double clutch, single clutch, and "float" the gears.
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Instructions
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Double Clutching
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From a stopped position, put the transmission in first, and slowly release the clutch. The tractor-trailer will begin moving. When your foot comes completely off the clutch, slightly press the accelerator.
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Let off the accelerator and quickly pump the clutch once, let it out, then push it down and hold it while you drop the shifter into the second-gear position. It should slide in easily and noiselessly. If it grinds, your rpm is either too high or too low for that gear.
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Advance through the rest of the gears using the same double-clutching procedure. If you run the rpm's a little higher than the shift point before you double clutch, your engine should have just enough time to settle down on the shift point, and you can enter the gear smoothly.
Single Clutching
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From a stopped position, put the transmission into first gear, slowly come off the clutch and begin to roll.
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Step on the accelerator to bring the rpm's up slightly. Release the accelerator pedal. Rest the shifter against the gear so that you can feel the shifter rubbing the gear, but don't press so hard that you hear it grind.
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When the gear just about stops rubbing, simultaneously push in the clutch and drop the shifter into gear. Use this same technique for all of the gears.
Floating Gears
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From a stopped position, put the transmission into first gear. Slowly let out the clutch, allowing the tractor-trailer to start rolling. This is the only step where you will use the clutch.
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Step on the accelerator to bring the rpm's up slightly. Release the accelerator pedal. Rest the shifter against the gear so that you can feel the shifter rubbing the gear, but don't press so hard that you hear it grind.
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At the moment you feel the gear stop rubbing the shifter, push the shifter into gear without using the clutch. The idea behind floating gears is to shift without the clutch. Floating gears requires that you have a very good feel for where your truck's shift points are.
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Tips & Warnings
Each truck's shift point is different, so you'll have to experiment with finding what the shift point for your truck is.
Don't accelerate while the clutch is fully or partially engaged. Wait to accelerate until you've let out the clutch completely.
Floating gears and, to a lesser degree, single clutching have the potential to wear out a transmission quickly if they are not done with precision. Many trucking companies do not allow drivers to float gears on their equipment.
References
Resources
- Photo Credit truck stick shift image by Aditia Patria Warman from Fotolia.com
