Behind the Wheel of a Big Rig

Double-Clutching
Shifting (behind only backing and navigating tight turns without running over curbs and mailboxes with trailer tires) is the most difficult skill to master. Virtually all big-rig transmissions are manual shift. Because the transmissions must handle so much power, most 18-wheeler transmissions—like racecar trannies—lack the synchronizers found on manual-shift production cars. So truckers are required to double-clutch when shifting both up and down the gears. Or else they shift without using the clutch.


Double-clutching is a skill that was, decades ago, virtually mandatory for all drivers—especially performance and race drivers—but is now about as critical as being able to rapid fire a muzzle-loading musket. Except when you're driving a big-rig.


The procedure for double-clutching: push in the clutch, move the shift lever to neutral, release the clutch, match engine speed and those of the transmission input and output shafts by either pressing the accelerator (if downshifting) or allowing engine speed to fall (if upshifting), push the clutch in, move the lever to the next gear.


Remain in neutral too long or hurry between gears and you'll grind cogs and wind up in neutral. When not in gear, the truck will either lose speed (if on level ground) or gain speed (if going downhill).


Grades imperceptible in cars become Everest-like when you're pulling 80,000 pounds. Or, worse, the weight is pushing you. If the rig loses or gains speed by a few mph, you'll have to give up chasing the gear you were after and hunt for another. It may be up or down. It may be two up or two down. Shifting without touching the clutch can be easier, but you still must match engine and transmission speed.