Allison announced last week that upgrades being made to existing PTS transmission models in 2011 will include new features that allow for a direct connection between the engine and automatic transmission to avoid slippage and to increase fuel efficiency.
An Allison spokesman confirmed there are new electronic control features available with 2011 model-year transmissions, but there are no new transmission models. The new Increased Torque Converter Lockup feature for Allison 1000/2000 Pupil Transport/Shuttle Series are targeting improved fuel economy for specific vocation vehicles such as Type A school buses.
Lock up occurs to connect the transmission input directly with the engine output, eliminating the energy loss of the traditional converter. Converters traditionally work with a fin drive and driven system that is not a direct connection, explained Denny Coughlin, retired fleet operations manager at Minneapolis Public Schools and owner of private consultant group School Bus Training Company.
But heat build-up, friction and slippage can lead to a certain amount of loss in the traditional converter drive system. The new Increased Torque Converter Lockup feature for the automatic Allison 1000/2000 series is designed to create a direct contact between the engine and the transmission, similar to a regular clutch system.
Allison also announced that its 3000 PTS models for large school buses are now available with new Low Speed Grade Assist to provide improved performance and reduce heat generation when climbing grades.