Eaton transmissions are designed for use in heavy-haul interstate trucks, and are in many makes and models of tractor-trailer truck rigs. Every Eaton transmission has a specific number of gears, such as the Eaton 10, Eaton 13, the Eaton 15, and the Eaton 18. Eaton transmissions have a gear ratio splitter lever allowing cycling through the gear pattern a second time to access the higher gears, which you do after shifting through all of the gears in "low" ratio.
Start the vehicle and allow it to idle until reaching operating temperature. To do so, depress the clutch and place the Eaton transmission into "Neutral." Some Eaton-equipped vehicles have an ignition safety switch in the clutch, so you may have to press the clutch to the floor while turning the key to start the vehicle.
Look at the gear pattern imprinted on the shifting knob and note the number of gears, beginning with gear 1. Note that each gear on the knob has the low gears displayed in a light color, and the higher gears in a darker color immediately below the low gear label. An Eaton 13, for example, will show a "1" and a "7" where first gear is displayed. The dual-gear labels may differ from this example depending on the gear pattern of the transmission.
Press the clutch pedal to the floor and move the shifter lever into first gear. Let the clutch pedal slowly raise from the floor while adding a very small amount of pressure to the accelerator as the vehicle begins to roll forward. Once the clutch has been let out fully, accelerate the vehicle until between 1,300 revolutions per minute (RPM) and 1,500 RPM (reading 13 and 15 on the gauge) and hold it there until ready to shift into the next gear.
Release the accelerator pedal and move the shift lever to "Neutral" at the same time. Allow the RPM gauge to drop to between 600 and 700 and gently move the shift lever into the next gear. Slowly apply pressure to the accelerator, taking the vehicle back up between 1,300 and 1,500 RPM once again. Hold until ready to shift into next gear. Continue shifting up until reaching the highest "low" gear on the given Eaton transmission.
Release the accelerator while at the same time moving the gear lever into "Neutral" position. Lift or slide the gear splitter lever to activate the high gears. Move the shifter over and into first gear position, which will be the first gear in the high gear ratios. Shift through as many of these gears as necessary to arrive at the desired vehicle speed where the RPM gauge can stay between 800 and 1,000 RPM at that given speed.
Shift through the gears backwards when planning to come to a stop. To shift down each of the gears, allow the vehicle to drop to between 600 and 800 RPM when in each gear, then let off the accelerator while moving the gear lever into "Neutral." While in "Neutral," tap the accelerator enough to swing the RPM gauge needle to between 1,300 and 1,500 RPM and slide the shifter into the next lower gear. Allow the transmission to slow the vehicle at each down-shift and continue this step until reaching the lowest "high" gear on the transmission.
Slow the vehicle down in the lowest gear, with the ratio splitter in "high," until the RPM gauge reaches between 600 and 800 RPM. Let off of the accelerator, then move the shift lever into "Neutral" position. Switch the gear ratio splitter lever back to "Low" to move through the lower gears while shifting down even further. Move the gear lever all the way to the right, preparing to move it into the highest "low" gear. Tap the accelerator, while in "Neutral," to swing the RPM gauge to between 1,300 and 1,500 RPM, then shift into the gear.
Apply pressure to the brake pedal between each of the shifts, allowing the transmission to perform the majority of the work slowing the vehicle, using the brake only as an assist or for rapid emergency stops. Using the brake as an assist, shift down through all of the gears until reaching the lowest. After shifting into the lowest gear with the ratio splitter lever in "Low," reduce the vehicle speed until at idling speed. Press the clutch and brake to finish bringing the vehicle to a stop, then shift the gear lever into "Neutral."
Most experienced drivers are able to easily shift Eaton transmissions without using the clutch while the vehicle is moving. If not experienced, reduce wear and tear on the gears in the transmission by using the clutch every time when taking the shift lever out of gear, and every time when putting the lever into a gear. This clutch use is called "double-clutching" and, although not mandatory, can extend the useful life of the transmission.