By Paul Abelson
Making frugal decisions isn't necessarily the cheapest route, even as public works departments operate on ever-tighter budgets. It's often wise to spend more upfront for greater long-term value, especially when buying equipment. Automated and automatic transmissions, while initially more costly than manual models, improve fuel economy and reduce long-term fleet maintenance costs.
Automated transmissions cost several thousands of dollars more than manuals, and automatics may be more than $10,000 higher. However, the cost of automatics is justified when constant torque is needed for heavy hauling or hilly terrain. Automatic transmissions also reduce the shock load on drive trains and suspensions, and result in less damage to vehicles.
Fleet managers report lower maintenance costs with both types of transmissions, due to smoother operation and the elimination of missed shifts. Both also save the time and money associated with training drivers how to shift with manual transmissions.
Automatic transmissions have long been criticized for poor fuel economy,. But manual and automated transmissions have a coast-down period during every shift, losing speed that must be regained. Automatics can actually improve gas mileage in urban operations requiring a good deal of shifting.
Automatic transmissions have hydraulic torque converters and planetary gears. Like the transmission in a car, a torque converter uses fluid that allows slippage when at idle, then adjusts vanes to vary torque and rpm. Because these transmissions use hydraulics in every gear, it takes fewer gears to cover the operating range. For fuel economy, the converter locks up at speed.
More than a decade ago, Eaton introduced the Autoshift transmission, a computer-controlled version of their line of proven manual transmissions. Autoshifts use the principle of floating gears, but a computer does the shifting and controls engine rpm. This technology opened up the use of automation to all trucking.
Automated transmissions are based on manual transmission designs. The transmission and engine computers coordinate throttle movement and the actions of the X-Y actuator (the device that moves the shifter mechanism). It replaces the familiar gear shift handle.
Autoshift needs the clutch to disengage when stopping or to engage when starting. Eaton's latest UltraShift brand models have computer-activated clutches and two pedals (throttle and brake). Tests have shown that these models get up to 7.5% more miles per gallon than manuals.
UltraShift offers numerous safety features, including Hill Assist, which minimizes rollback when going from brake to accelerator on grades up to 10%. Minimizing rollback prevents crashes that, while minor, happen too frequently and affect maintenance, insurance rates, and safety records. Creep Mode lets drivers maintain speeds as low as 1 mph with feet off the pedals — in both forward and reverse — up and down grades.
|TYPES OF TRANSMISSIONS
MANUAL — Users operate a gear shift handle, or “stick shift,” to match the engine's operating rpm with truck speed and multiply the engine's force to meet power requirements.
Three models of UltraShift Plus are available. The 10-speed Vocational Construction Series (VCS) comes with torque ratings of 1,450 to 1,750 pound-feet. With three reverse speeds and an overall range of 19.68:1, it's designed for on- and off-highway operations.
The 11-speed Vocational Multipurpose Services (VMS) has the greatest overall ratio at 35.73:1 and the same torque ratings as the VCS. It's exceptional for creeping and low-speed maneuverability.
For maximum power applications and extreme gradeability, the Vocational Extreme Performance (VXP) has ratings from 1,450, 1,650, 1,850 and a whopping 2,250 pound-feet of torque. It has 18 forward and four reverse speeds, and an overall ratio of 19.73:1.
As great as their features seem on paper, these transmissions have to be driven to be fully appreciated. There is no way to describe the feeling of starting from a full stop on an 8% grade with absolutely no rollback, when loaded to 80,000 pounds.
On a recent test-drive, I was amazed to find that I could creep ahead or in reverse at ½ mile an hour. I also took a 160,000-pound., 11-axle Michigan trailer up a 15% grade from a 50-mph running start. The VXP transmission went from 16th to second gear in just three steps with never a shudder or shake.
The entire family of UltraShift Plus transmissions represents a new generation of automation. More importantly, it offers an alternative to traditional automatic transmissions for frugal decision-makers.
— Paul Abelson (email@example.com) is a former director of the Technology and Maintenance Council (TMC) of the American Trucking Associations, a board member of Truck Writers of North America, and active in the Society of Automotive Engineers.
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