Behind the Wheel of a Big Rig

Behind the Wheel of a Big Rig

Familiarity breeds content when sharing the road with 40 tons and 18 wheels
on

Imagine you're motoring down a curvy backroad. It's so narrow that when you're 18 inches away from the fog line on the right, the left side of your vehicle is no more than that away from the centerline. Touching mirrors with passing vehicles is a real concern. Your brakes promise little stopping power. Your tires don't provide much grip, which is good-the vehicle is so top heavy that sticky tires would result in a tip over.

And you're going 120 mph.

At least that's what it feels like going 70 mph down a gently winding interstate highway behind the wheel of an 80,000-pound 18-wheeler. I've reached 155 mph on the German Autobahn-my first freeway experience in a big rig felt much faster.

Nervous Brake Down

Drivers of 18-wheelers are told to look at least 12 to 15 seconds ahead. On the interstate, that's about a quarter of a mile. If you're herding a loaded 53-foot trailer, 1,300 feet doesn't feel like a big cushion, and for good reason. Bringing a big rig to a halt takes about half again as long as the poorest-stopping SUV. (Consider that before cutting in front of an 18-wheeler.) And the trucker's confidence isn't helped by a half-second delay between when the driver goes for the brakes and pressurized air finally causes the brake shoes to contact the drums. (Your hydraulic brakes work instantaneously.)

In a big-rig, even mundane tasks, such as driving through a toll booth lane, become major challenges. Approaching a toll booth not long after I'd earned my Commercial Driver's License, I calculated that my truck was the proverbial camel attempting to go through the eye of a needle-we'd need a miracle to make it. Then I watched another truck successfully navigate the opening. I positioned my left mirror about four inches from the booth and cringed as I anticipated the impact of the right-side mirror. It didn't come. I asked my co-driver how close it was on that side. "Aw, ya had a couple inches." For a long time, when another big rig passed to my left, I had to fight the urge to tuck in my left elbow.

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.

Splitting Gears

Heavy trucks have multiple-ratio drive-axles, much like high- and low-range found on most four-wheel drives, except that you actually use both during everyday driving. Truckers must manipulate a switch or switches to change ratios; it's called splitting. Some axles are split after the driver rows through the conventional "H" pattern positions. Others demand a split between every gear. For the former, the split comes after, usually, Fifth gear. Flip the switch and the gear position that formerly was First now is Sixth, Second becomes Seventh and so on. With a split-every-gear system, to shift from First to Second, the gear lever is left stationary and a switch on the lever is thrown. When it's time to go to Third, the switch is moved back to its original position and the shift lever is moved back to the 3-4 position. A flip of the switch gives you Fourth. Repeat through all gears. There will be a quiz. That's not true: There will be many quizzes.

A popular heavy truck powerplant is Detroit Diesel's turbocharged 12.7-liter inline six-cylinder. It makes 380 horsepower at just 1,800 rpm and a gargantuan 1,350 pound-feet of torque at a very low 1,200 rpm. (For comparison, the Dodge Viper boasts 500 horsepower at 5,600 rpm and 525 pound-feet of torque at 4,100.) A diesel offers so much torque that to get 40 tons rolling all you have to do is release the clutch. No throttle is needed. In fact that's contraindicated. However, the diesel's rev limiter kicks in at about 2,200 rpm. Depending on the transmission and load, the driver must go through nine or more gears to reach 45 mph.

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