The early days of any new technology are full of early-installment weirdness. Smartphones used to have physical keyboards, television once used 60-line broadcasts, and automatic transmission-equipped cars didn’t always let you throw it in a shifter position called park. Say what?
It should go without saying that using a car’s parking brake to lock some of its wheels while parked is a good idea. After all, these beefy mechanical systems should stop two tons of metal and glass from wandering off to tour the local estuaries, do some landscaping, or get into other mischief. However, redundancy is important in any safety system, so it’s best to not trust the parking brake alone. [Editor’s Note: I once had my stickshift Jeep XJ’s park brake “let go” on what I thought was flat ground. It wasn’t. I walked out of my friend’s house and found my Jeep in the neighbor’s yard. -DT].
Whereas leaving a manual gearbox in gear directly connects the drive wheels with the engine to prevent vehicle movement using the engine’s compression, conventional hydraulic automatic transmissions use a fluid coupling to connect the crankshaft to the transmission’s input shaft, so they’re not rigidly connected, meaning they need an extra bit of hardware to lock the drive wheels. That’s where the parking pawl comes in. It’s a sturdy piece of metal that locks into a toothed wheel on the transmission’s output shaft, stopping the drive wheels from rotating. These pawls are typically the most robust things in automatic transmissions, so they’re unlikely to break. However, engaging the parking pawl wasn’t always as simple as throwing the gear selector into park.
While early Hydramatic transmissions did feature a parking pawl, operation isn’t exactly intuitive by modern standards. See, the parking pawl on these transmissions only engages with the gear selector in reverse and the engine off. Sure, some owners of modern high-performance cars with weird gear selectors would figure this cached parking position out, but without a dedicated park position on the shifter, locking the output shaft of an early Hydramatic seems like a needlessly obfuscated process. For a conventional automatic transmission with a dedicated park position on its shifter, we need to jump forward eight model years from the launch of the Hydramatic to the 1948 Buick with its available all-Buick Dynaflow automatic transmission, referred to in a period brochure as having “the first positive parking lock ever provided in a liquid-coupled drive.”
By modern standards, the Dynaflow two-speed automatic was a weird transmission, seeing as it started in its high-range direct drive ratio and used its torque converter to creep off the line. The resulting effect was the aural monotony of a car with a continuously variable transmission but without any of the CVT efficiency. You could lock the Dynaflow in first until about 60 mph or until enough valve float to un-sink the Edmund Fitzgerald is achieved, but we aren’t exactly talking about the pinnacle of sportiness here. The Dynaflow is rudimentary technology from a time when “treadle” was an acceptable word to use for “pedal” in automotive marketing materials.
Still, sprouting from the steering column of Dynafl0w-equipped vehicles was a gear indicator, and it read PNDLR. At last, a separate, distinct single-purpose parking pawl setting for automatic transmissions! Now that’s an innovation we can all get behind.
An honorable mention goes to Packard coming out with its Ultramatic automatic transmission of 1949. While it still didn’t automatically shift between low and high ratios, it featured a dedicated parking gear and a locking torque converter, the latter feature improving drivability substantially over Buick’s Dynaflow.
As a period Packard ad claimed, “You’ll never be annoyed by jerking or clunking, or “racing engine sensation”…never bothered by gas-wasting slippage at cruising speeds…never “outsmarted” by complicated automatic controls.” That certainly seems like a great leap forward from other automatic transmissions of the time with non-locking torque converters. As for the shift pattern on this bad boy, how does PNHLR sound? Having an “H” for high gear and reverse way down low on the selector totally isn’t strange, right?
Alright, so this was still the early days of the hydraulic automatic transmission, but wacky shift patterns would soon be fixed by Ford with the Fordomatic Drive automatic transmission, and the rest, as they say, is history. Today, throwing an automatic transmission in park is a no-brainer, but it took years for automakers to figure that out. Let’s be thankful this took less time than figuring out the modern pedal arrangement of throttle on the right, brake in the middle, and clutch on the left if so equipped.
A programming Note: This is The Autopian’s first installment of Invention Hour, where we talk about various car inventions, as well as fun car features and also odd failure modes.
(Photo credits: Buick, Packard, Ford)
Support our mission of championing car culture by becoming an Official Autopian Member.