As
the graph comparison below shows, selecting the Allison transmission’s
tow/haul mode when reducing speed provides approximately 150 retarding
horsepower. In the same mode, with the addition of a Pacbrake PRXB,
the retarding ability is almost doubled, providing the most effective
speed reduction possible without the need for service brakes. Allison
transmissions will automatically downshift to attain higher RPM to
aid in retarding, but with a Pacbrake PRXB, higher RPM is not as critical
due to the unique modulation design.
