Commercial vehicles such as refuse compactors, concrete agitators, tippers, fire truck pumpers, or a hydraulic crane arm often feature specialised equipment to perform specific tasks often use live drive Allison transmissions. This equipment typically needs to take power from the engine to operate hydraulic or mechanical equipment, whilst the vehicle is moving.
Allison fully automatic transmissions are available with power take off (PTO) drive provisions in a variety of positions. PTO’s can be installed and operated as a single unit or in pairs, and the following configurations are possible:
- Side-side PTO option: has PTO pads at approximately four o’clock and eight clock viewed from the rear of the transmission.
- The top side PTO option: has the PTO pads at approximately one o’clock and eight o’clock viewed from the rear of the transmission.
This principle of operation means the power take off has the following values:
In most Allison transmission models, the PTO drive gear is driven directly by the engine (live drive), while manual or automated manuals typically use output PTO provisions.
Ease of integration: manual and automated manuals require a dedicated interface with the vehicle pneumatic system; an Allison PTO engages directly via Allison transmission fluid pressure. The Allison Transmission Control Module (TCM) controls all basic PTO functions.
Power take off: As the PTO drive gear is constantly driven by the engine, the Allison Transmission can provide continuous and higher power takeoff ratings than is possible with a manual or automated manual gearbox. Two PTO’s can be used simultaneously.
Pump and roll: With an Allison, the PTOs are driven directly by the engine, and they can operate whilst the vehicle is in motion, allowing specialised equipment to be activated when driving, and making operations such as pump and roll possible.
Allison programming functionality can be setup to protect the hydraulic components which can also equate to big dollar savings.
Functionality and safety features can be used to limit the PTO operation by adjusting road speed (calculated from the output RPM, diff ratio and tyre size) or engine RPM.
Operators can use the gear indicator with the PTO function to limit the PTO operation to specific gear or gears (i.e. 1st neutral and reverse or just neutral or any specified range)
The drivers capacity to turn on the PTO can be limited if the engine RPM is high, which could cause damage to the PTO, transmission or the hydraulic components.
Using the PTO on an Allison Automatic Transmission provides greater vehicle utilisation options, pump and roll (live drive), increased efficiency and more power to get the job done, when it counts.