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Low Gears driving down a hill

I am going on a camping trip this weekend and I thought I’d get some insight to mountain driving. I understand that going down a steep hill, one should stay in the lower gears to slow the car and prevent constant braking and brake fade. However, what is the mechanics behind this? In lower gears, what prevents the car from continuing to gain speed as I am going down the hill. Let’s say I am in 1st gear and my car max out at 20 mph. How is it that the car stays at 20mph and what prevents the car from flying down a steep hill? Won’t the kinetic energy of the car eventually speed up car past 20mph? Thanks.


That’s how an engine works. It sucks air and fuel mixture, squeezes it, ignites it to get a bang that pushes the car, and blows it out so it can start sucking in a fresh mixture. When you put it in a low gear with your foot off of the throttle, usually, there’s no fuel injected. No fuel means no bang. The sucking of air through the closed throttle plate requires energy. Lower the gear, more suckings happen, and more kinetic energy is transfered from the car to the suckings.

However, there’s no guarantee that you will stay below 20 mph, as far as a manual transmission is concerned. If the hill is steep enough and the suckings do not occur often enough, you can push the engine past its maximum designed speed (redline). It is your responsibility to keep an eye peeled for the engine speed and use your brake pedal periodically to slow it down as necessary. Modern computer controlled automatics may upshift to prevent engine damage. But it is still a good habit to drive as if the protection is not there.

BTW, 2nd gear is generally as low as you want to go for regular driving. You don’t want to use 1st gear unless it is roller coaster steep.

I first heard that as Snort,Squeeze,Pop,Wheeze. Probably was someone like Smokey Yunick that came up with this saying

“suck squeeze bang blow” That’s the first time I have seen those words used in an explanation that wasn’t rated “R” .