The AT545 is the most popular transmission in school buses in the 1980s and 1990s and is generally a very reliable unit if you accept its limitations. Nearly every bus equipped with the Cummins 5.9 or Navistar T444E in a front engine configuration will be using the AT545, including all Bluebird TC2000 front engine models (caveat: a few unicorns with MT643 have actually been spotted in the wild, but they are extremely rare!) it is also common with lower rated versions of bigger engines like the DT466 and CAT 3216.
The service manual covers normal maintenance, component identification and testing procedures, and the complete overhaul process. This manual includes the entire family: AT540, AT542, AT543, AT545, AT1542, and AT1545.
