It is a Mack manual transmission. It features in Mack tradition a 5 speed main box and a 2 speed transfer case integrated into a single package. The transfer case is a separate casting bolted to the back of the main box, but the output shaft is a single long shaft reaching through both boxes. The main box is of the constant mesh type in that the gears are always engaged and a small shifting spline slides to lock the proper gear to the output shaft. It is not a synchro-mesh transmission, in that the extra hardware to synchronize the gears is not present.
