How to Shift a 15-Speed Transmission

by Kelvin HayesUpdated June 08, 2023
itstillruns article image
Semi image by Andrew Breeden from

The shift pattern on a 15 speed transmission can be visualized like a three story building. On each level, you have five possible gears, defined as a "range." The first floor is "deep lo" or deep reduction. The second floor is "low range" and the third is "hi range." As you shift through the gears in each range, you'll move to progressively taller gears, with less torque, but allowing for a higher top speed.

1. Push the clutch pedal in

Push the clutch pedal in and shift into the farthest left and back slot, this is deep lo 1. With the clutch depressed, ensure that the split switch on the head of the gear shift is moved the the left, engaging the deep lo range.

2. Release the clutch

Release the clutch, apply the accelerator and begin forward. As the engine RPM gauge approaches the red line, depress the clutch and shift straight forward to deep lo 2. Again, as the RPM nears the red line (no need to over rev the engine), shift back and to the right to reach deep lo 3. Forward for deep lo 4 and back/to the right for deep lo 5.

3. Flick the split switch to center

Flick the split switch on the gear shift head to the center position. This raises the range from deep lo to low range. Do this as the engine again reaches near the red line. With the switch moved to the center, you may now move the gear shift all the way to the "1st" position, found and the furthest back left position. This gear is Low 1. Repeat the shift process outlined for deep lo, as the pattern is the same.

4. Flick the split switch to hi range

Flick the split switch to the right one more click to engage the hi range. This should be done as you reach higher RPMs in the low 5 gear. Then, move the shifter back to hi 1. Repeat the shift process outline for the deep lo range. You may reverse this shift pattern to down shift and slow down without the use of the brakes.

More Articles

article divider