Ease on Down the Road

By on October 28, 2009
RoadKing Mag

When I learned to drive a truck in the ’80s, the school had me spend the first third of the program in the yard, just learning how to shift gears. Unlike automobile transmissions, trucks have no synchronization. Drivers must learn to “double clutch” — to match engine rpm with vehicle speed, then select the right gear for the situation.

It’s easy enough to do until you get on a hill where speeds change more quickly, requiring faster reaction time. Get it right, and you keep control. Get it wrong and you could find yourself in neutral, unable to get back in a gear. That could be the start of a runaway truck situation.

Big rigs depend on the engine to help keep control. Diesel engines’ higher compression ratios help retard the truck, and engine brakes, also called Jake Brakes, help on steeper grades. But they cannot work if the truck is in neutral.

When stuck in neutral, the best thing is to pull onto the shoulder, stop the truck and start all over, even if it means creeping up or down a hill in first or second gear. But that assumes you can stop, that your brakes can handle the truck’s weight and the steepness of the grade.

Experienced truckers know when they can complete a shift and when they might get in trouble. They develop the skill to avoid rollback when starting on a grade. This prevents crashes that, while often minor, affect insurance rates and safety records. Skilled drivers also learn to feather the clutch and throttle in order to creep forward in snarled traffic or back gently up to a loading dock or down into a pit.

Nobody starts out as an experienced driver though.

Automated help
Eaton Corporation introduced automation to truck transmissions in the 1990s to prevent driver fatigue. Research showed that OTR drivers made more than 90 percent of their shifts between the top two gears, so Top-2 became the first automated manual transmission. It reduced leg and shoulder soreness and helped drivers stay alert but solved none of the other transmission-related problems.

Although not recommended, many experienced drivers “float” the gears. They shift into neutral without using the clutch, lifting the throttle to reduce torque and nudging the shift lever. They then adjust engine rpm to match vehicle speed in the next gear, and, at the instant when everything aligns, put the lever into the next gear. With practice, they get it right almost all the time. When they don’t, the gears grind and they go back to the clutch.

Eaton engineers developed computer programs to do exactly what experienced drivers do: float the gears. Instead of a shift lever, it uses actuators. The clutch was left for starting and stopping, and the computer did the rest.
Computers don’t get it right most of the time. They get it right every time. Two positions, Hold (now “manual”) and Low, let the driver have control when they want it, telling the computer when to shift up or down, stay in gear or allow only downshifts. But if a shift cannot be completed, the computer won’t even start it. No more getting hung out in neutral.

A few years ago, Eaton released UltraShift, which let the computer actuate the clutch. The new clutch-less, two-pedal transmission made driving easier, but safety and control issues still remained unaddressed.

No longer. In September, Eaton introduced UltraShift Plus. The entire new transmission line features automated clutch technology and software that uses grade sensing, weight-computation and throttle position and movement sensing. For OTR operations, Linehaul Active Shifting (LAS) models have gear ratios and software designed to improve fuel economy and enhance low speed control. Other on-highway models include Multipurpose High Performance (MHP) and Multipurpose Extreme Performance (MXP). There are also three vocational models for dump trucks, mixers and other specialized trucks.

As great as the features seem on paper, these transmissions have to be driven to be appreciated. There is no way to describe the feeling of starting from a full stop on an 8 percent grade with absolutely no rollback — in a truck loaded to 80,000 lbs. I was amazed to be creeping ahead or backing up at one-half mile an hour, even on grades. I also took a 160,000 pound Michigan trailer (11 axle combination) up a 15 percent grade. The MXP transmission took the rig smoothly from 16th down to 2nd in just three steps, with never a shudder or shake.

The UltraShift Plus transmissions represents a new generation of automation. More important, they offer safety, control and economy not possible just a few years ago.

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