There’s little doubt that drivers ultimately hold the key to fuel economy. Once the most efficient engine and drivetrain specifications have been developed for a fleet’s particular operation, maximizing fuel savings is put, quite literally, in the hands of the driver.
That is why, perhaps, a growing number of fleets are opting to take the driver out of the equation, to effectively remove his or her hands from the process by specifying automated manual or automatic transmissions.
With these transmissions, the burden of shifting is removed, allowing the vehicle to operate as efficiently as possible for as much of the time as possible. That process improves fuel economy. It can also, manufacturers are quick to point out, reduce wear and tear on transmissions and driveline components, and even help extend brake life.
In addition, many users of automated manual and automatic transmissions firmly believe that safety is enhanced with these technologies. It is a simple matter, they say—without the need to perform multiple, and at times complex gear changes, drivers can stay focused on the road and keep both hands on the wheel.
Along with their traditional manual transmission offerings, vehicle manufacturers now offer a growing range of automated manual and automatic transmissions for trucks.
Allison
Allison Highway Series automatic transmissions for engines rated from 165 to 565 HP and 420 through 1,800 ft./lbs. of torque can be spec’ed on vehicles above 14,000 lbs. GVW. Models include close and wide ratio versions of the 1000 HS, 2100 HS, 2200 HS, 2300 HS, 2350 HS, 2500 HS, 2550 HS, 3000 HS, 4000 HS and 4500 HS. The Highway Series transmissions feature Load-Based Shift Scheduling (LBSS) that automatically selects between Economy and Performance shift schedules based on the vehicle’s actual payload and the grade on which it is operating. Also part of the design are prognostics to monitor various parameters, and several operating features such as Reduced Engine Load at Stop (RELS) that automatically reduces the load on the engine when the vehicle is at a full stop (available on 3000, 4000 and 4500 HS models), Shift Energy Management (SEM) for engine/transmission integration, Automatic Neutral on the Park Brake, and Retarder Enable Electronic controls that blend functions of the transmission, retarder and service brakes.
Eaton
Eaton offers a number of versions of its new UltraShift PLUS automated transmissions for linehaul, heavy-haul and vocational chassis. The UltraShift PLUS family includes Linehaul Active Shifting (LAS), Multipurpose High Performance (MHP), Multipurpose Extreme Performance (MXP), Vocational Construction Series (VCS), Vocational Multipurpose Series (VMS), and Vocational Extreme Performance (VXP) models. All of Eaton’s UltraShift PLUS transmissions, available in overdrive and direct-drive models, feature a new self-adjusting electronic clutch actuator.
Intelligent shift selection software employs grade sensing, weight computation and driver throttle commands to make shift decisions. Other features include a Hill Start Aid feature, automatic, manual and low mode selection options, a creep feature for maneuverability with continuous low-speed control, six- and eight-bolt, as well as thru-shaft power take off (PTO) options, and an oil level sight glass to check fluid levels.
Freightliner
The Freightliner AMT3 Automated-Manual Transmission for Business Class M2 vehicles is available on the OEM’s Class 6 and 7 trucks. Included are direct and overdrive versions of the six-speed models. The direct drive version is rated from engines up to 520 ft./lbs. of torque and vehicles with a maximum GCW of 33,000 lbs. The overdrive version of the transmission is for use on vehicles up to 40,000 lbs. GCW with engines rated to 660 ft./lbs. of torque.
The AMT3 from Freightliner uses a Transmission Control Unit (TCU), which employs intelligent shift logic to evaluate road, grade and load conditions, to manage clutch control and gear shifts. The transmissions come with the manufacturer’s SmartShift lever, mounted to the steering column, so drivers can shift manually or allow the AMT3 to make shifts automatically.
Mack
Mack Trucks’ mDRIVE automated manual transmission is engineered to work exclusively in the OEM’s Pinnacle model highway tractors powered by Mack MP7 and MP8 engines. mDRIVE has 12 forward and four reverse speeds in direct drive or overdrive models and is available in two versions. The Fleet package includes basic shifter controls, with Grade Gripper hill start assist and MackCellerator kick-down feature options. MackCellerator drops the transmission one gear (while synchronizing engine RPM) when the accelerator pedal is sharply depressed to maximize acceleration in passing situations. The Premium package consists of a shifter with more features, including manual shift inputs, performance and economy modes, plus Grade Gripper and MackCellerator. mDRIVE is available with two optional rear-mounted power takeoffs (PTO). In addition, mDRIVE is offered with Cruise’n Brake, which limits engine brake operation while in cruise control; Low Speed Modulation control, which enables very low vehicle speeds when using the brake pedal; and Auto Neutral, which automatically shifts the transmission to neutral if the engine has been shut off while in gear or after four minutes of idling with the parking brake applied.
Volvo
Volvo I-Shift is a 12-speed, automated mechanical transmission that is designed to be integrated with all Volvo engines. Available in five versions, I-Shift direct and overdrive models are offered for linehaul, heavy haul, construction, distribution, and pickup and delivery operations.
The third generation of Volvo automated mechanical transmissions features a grade sensor, Kick-Down Mode for instant power and maximum acceleration, Performance Mode for maximum gradeability, and a Brake Program Mode for maximum retardation. An optional feature called Eco-Roll also improves fuel economy in the top gear, according to the company.
