Author Topic: Two Features On Old Automatic Transmissions That Don't Exist Today  (Read 712 times)


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Back in the 1940's and 50's car manufacturers made automatic transmission's with two unique features you don't see today. The first feature allowed a car to be push started when the battery was low, or for whatever reason electric started wasn't working. The second feature allows the car to be rocked back and forth by using engine power and quickly shifting the transmission from forward to reverse and back again to create a rocking motion to help when a car was stuck. I don't know the exact dates when transmission features like this started and ended, but these features were more important before there was a USA Interstate Highway System.

General Motor's first Hydramatic automatic transmission placed reverse and low gears right nest to each other (see image below) in the shifting pattern to allow the driver to quickly shift back and forth from these two positions in order to create a rocking motion when your car is stuck in a rut. You can't do this as easily on a modern automatic transmission. I was stuck once driving a pickup truck equipped with an automatic transmission and I was able to rock the truck back and forth, but I had to apply the brakes at the high points, which would stop the vehicle so I could shift gears and wait for the transmission to engage, then go and repeat until I was free.

General Motor's connected a second automatic transmission oil pump to the output shaft on their Hydromatic transmission. When the transmission was placed in low, and the car was being pushed with the engine off, it allowed the automatic transmission to engage and rotate the engine. This resulted in the engine turning over so the car would start. This method of starting a car was called "Push Starting." According to the video below, the drive train would engage around 15 mph. You can't do this on a car equipped with a modern automatic transmission.

I thought the following video was interesting because it shows cars from this era actually using these two features.

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« Last Edit: January 02, 2020, 06:13:57 PM by smallengineshop »
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