The two speed rear axle electric shift system utilizes a two speed rear axle shift motor to shift axle range either up or down. The shift motor is controlled by a two speed rear axle shift relay. Circuit breaker 22 supplies battery voltage during RUN or START through the ignition 3 voltage circuit to the two speed rear axle shift relay. When the two speed rear axle driver control switch is in the LOW position, the switch is open, the relay is de-energized, and voltage is present at the speedo adapter or the powertrain control module calibrating it for low gear.

When the two speed rear axle driver control switch is placed in the HIGH gear position, the shift motor relay control circuit is closed to ground, removing voltage from the speedo adapter/powertrain control module and energizing the two speed rear axle shift relay. The energized relay allows current to flow through the high gear shift motor control circuit to the shift motor. Inside the shift motor, current flows through closed contacts of the high range switch and motor to ground which starts the motor rotating. Current also continues from common motor terminal through a low range switch and to ground through the resistor. As the motor begins to rotate the gear, a cam pin (low range) on the gear ramps up and opens the low range switch. The path to ground is open and a diode prevents the speedo adapter/powertrain control module from being energized. The motor rotation continues to shift the axle to high range. As the shift is completed, a cam pin (high range) opens the high range switch, opening the circuit and removing power from the motor. Motor rotation is stopped quickly by means of dynamic braking through a resistor. At this point the gear will have rotated 180 degrees. A break in torque by the driver allows spring force to move the swivel pin and shift fork in the appropriate direction for axle range change. When the opposite axle range is selected by the driver, the process is repeated by the motor turning 180° in the same direction.

View the list of major components that make up the air operated two speed rear axle shift system below.

On manual transmission models, the two speed rear axle driver control switch is mounted onto the manual transmission shift lever. On automatic transmission models, the two speed rear axle driver control switch is mounted to the instrument panel or on the shift tower. The two speed rear axle driver control switch is positioned by the driver in order to operate the two speed rear axle shift motor at the rear axle. The driver selects the rear axle range by positioning the two speed rear axle driver control switch to the LOW or HIGH axle range.

The two speed rear axle shift motor is mounted to the differential carrier. The two speed rear axle shift motor consists of a motor, a gear controlled slider block, a high range switch, and a low range switch. The shift motor rotates a worm gear which turns another gear which moves an eccentric pin in the slot area of the slider block changing spring compression. The slider block uses spring compression to move a swivel pin and shift fork into the appropriate direction for axle range change.

The two speed rear axle shift relay is mounted to the crossmember in front of the rear axle housing. When the two speed rear axle driver control switch is in the HIGH range, a ground is supplied to the two speed rear axle shift relay. The two speed rear axle shift relay then actuates the two speed rear axle shift motor to the HIGH range. When the two speed rear axle driver control switch is returned to the LOW range, the two speed rear axle shift relay is de-energized. The two speed rear axle shift motor then returns to the LOW range.

The speedometer adapter is used to match the ratio of the speedometer to the ratio of the rear axle. The speedometer adapter gives an accurate speedometer reading when the rear axle is shifted from one range to the other. When voltage is present at the speedo adapter it calibrates for low gear and with the voltage removed the speedometer adapter reads the high gear of the rear axle.