For the U.S. auto industry, there were twists and turns on the path to the fully automatic transmission. Here’s a fascinating detour from 1933-35, the Reo Self-Shifter.

Just to be clear, the Reo Self-Shifter was not a fully automatic transmission. The system required a conventional clutch and clutch pedal for starts and stops, and thus it falls into the catch-all category of “semi-automatic.” But its upshifts and downshifts were automated, a remarkable development when the Self-Shifter was introduced in May of 1933. Just as remarkable, the transmission was engineered entirely in-house by Reo, one of the smallest automakers. Its production volume was less than one percent of that of General Motors, and its finances were severely pinched.

Developed by longtime Reo chief engineer Horace T. Thomas, John Bethune, and Albert B. Hays, the Self-Shifter represented an investment of $2 million and was protected by multiple patents. The unique mechanism could be described as two transmissions in one: A basic two-speed manual and reverse gearbox in the front, followed by a three-element planetary gearset with two forward gears. In normal driving, the car operated on the planetary gearset, shifting from low to high at 15 mph and downshifting at 5 mph via a centrifugal clutch (above). Shifts were said to be nearly imperceptible from the cabin.

The manual gearbox came into play when engaging reverse or for steep grades or other loads. For gear selection, an ingenious rack mechanism was operated by a flexible shaft and T-handle that mounted under the dash (above and below). In a sort of push-pull modified H-pattern, pulling the handle halfway out selected neutral, left and all the way out selected the special low, while reverse was engaged from neutral by pushing forward and to the left. But for normal driving, the handle was simply left in the straight forward position. While there’s a clutch pedal to operate for starting and stopping, there was no shifting once under way, and no shift lever on the floor, allowing polite three-abreast seating in the front.

For the May 1933 introduction, Self-Shifter was a no-cost option on the deluxe Royal3 and an $85 extra on the Flying Cloud. According to contemporaneous accounts, the transmission was perfectly reliable and worked just as advertised, but it did little to boost Reo sales. Reportedly, the company hoped to sell Self-Shifter transmissions and licenses to other automakers, but there were no takers in the midst of a depression. The Self-Shifter transmission was dropped for 1936, Reo’s final year in the passenger car business (see our feature here). The company was now focused on trucks, where it had a much more secure market.