Allison Bus Series
| Allison Bus Series | |
|---|---|
| Cutaway of Allison 4000-series transmission (marketed as B500) | |
| Classification | Automatic transmission | 
| Application | transit and highway buses | 
The Allison Bus Series are medium and heavy duty automatic transmissions for transit buses and highway motorcoaches designed and manufactured by Allison Transmission. Each of the six models in the Bus Series is available in 5 or 6 speeds with an integral hydraulic retarder as an option.