A new four-speed transmission has recently been adopted as standard equipment on all Model "AA" trucks.

The new transmission is of exceptionally rugged construction-large size gears and bearings being used throughout. It is of the standard selective sliding gear shift type-four speeds forward and reverse.

All gears and shafts in the new transmission are made from special heat treated chrome alloy steel.

The countershaft is carried on roller bearings. A roller bearing is also used at the front of the main shaft. Because of their effectiveness in carrying radial loads, the main drive gear and spline shaft are carried on ball bearings.

Gear Shifting

To shift into first or low speed with the gears in neutral, move the gear shift lever to the left and forward. To shift into second from low speed, move the lever straight back through neutral into second speed. To shift into third from second, move the gear shift lever forward into neutral, then to the right and forward into third speed. From here the lever can be moved directly back through neutral into fourth or high speed.

To shift into reverse from neutral press the release catch on the side of the lever, located just below the gear shift lever ball, and move the lever to the extreme right out of range of the forward speeds, then directly back into reverse gear. (See Fig. 778.) The release catch is easily operated by the driver's thumb, making it possible to go into reverse gear with one movement.

How the Transmission Operates

In low speed the power comes in through the main drive gear into No. 1 countershaft gear, then through No. 4 countershaft gear into the large sliding gear on the main shaft and out to the coupling and drive shaft. (See Fig. 779.)

In second speed the power comes in through the main drive gear into No. 1 countershaft gear, then through No. 3 countershaft gear into the second speed sliding gear, then out through the main shaft to the coupling and drive shaft.

In third speed the power comes in through the main drive gear into No. 1 countershaft gear, then to No. 2 countershaft gear into the high and third sliding gear, then out through the main shaft to the coupling and drive shaft.

In fourth or high gear the power passes directly through the main drive gear and main shaft, the same as in the Model ''A" transmission.

In reverse, the power comes in through the main drive gear into No. 1 countershaft gear, then through No. 4 countershaft gear into the reverse idler gear. From the reverse idler gear it goes into the low and second sliding gear, then through the main shaft to the coupling and drive shaft.