Part of Allison's World Transmission (WT) family of automatics, the MD 3000 and HD 4000 Series offer a range of benefits for operators, including proven performance, durability, less powertrain wear-and-tear and ease of operation. Perhaps most important, the MD 3000 and HD 4000 deliver superior control for drivers, a performance feature that is critical in situations where a few seconds can mean the difference between life and death.

Operational benefits of the MD 3000 and HD 4000 Series, and all of Allison's automatics, include safety, ease of driving and reduced driver fatigue and maintenance. With an Allison, the driver is free from clutching, shifting gears and watching engine speed.

The fully-automatic MD 3000 and HD 4000 Series give firefighters the power and acceleration they need to get the job done quickly and safely: essential characteristics when seconds count. The MD 3000 and HD 4000 Series feature a high-range lockup modification for split-shaft applications such as fire pumps, foam pumps and aircraft refueling pumps requiring high pumping horsepower. The feature, when in "pump mode," permits "full torque" powering of a fire pump at a constant speed for extended periods. It also ensures operator safety by keeping the transmission in high-range lockup while the truck is stationary at the fire scene. The units' PTO function can also supply power to electrical generators: a critical benefit in situations where external power sources have failed.

Electronic controls enable the MD 3000 and HD 4000 to shift at exactly the right point in the engine's fuel consumption curve for best fuel economy. The transmissions' early lockup feature maintains the highest possible mechanical efficiency through the closely spaced gear steps. This allows progressive shifting techniques in which engine speeds are reduced for higher efficiency and lower fuel usage.

The MD 3000 and HD 4000 use closed-loop logic to ensure smooth, well-timed shifts. Closed-loop logic allows the electronic controls to look at multiple parameters during the shift and make minute adjustments to match the shift to a desired profile stored in its memory. The logic then looks at these adjustments and re-sets parameters for the next shift. This adaptive feature allows the transmission to quickly compensate for variations in load, terrain and environment, and to adjust for clutch wear and engine power changes. The electronic control can be programmed to match the exact requirements of the job-shift sequence, shift timing, lockup, gear hold, retarder apply, and special vocational needs.

The planetary gear sets in the MD 3000 and HD 4000, a helical design, provide a dramatic reduction of in-cab and exterior sound levels compared with straight-cut gears.

Allison World Transmissions, including the MD 3000 and HD 4000, incorporate the latest technology in design, manufacturing techniques and diagnostics. All models feature an advanced hydraulic torque converter with lock-up clutch and integral torsional vibration damper and planetary gear package. Added value and operational benefits include smooth starts on any grade, uninterrupted full power shifts, quieter operation and reduced driver stress and fatigue for improved safety.

Emergency Vehicles

For emergency applications, Allison is building on its proven base of functionality by extending the automatic "value equation" through its 2000 SeriesTM, a transmission engineered to meet the specific demands of emergency vehicles.