Your Car's Transmission for Dummies

Planetary gearsets in an automatic transmission

Riddle us this: what happens when freelancers get hold of a (pretty much) correct source and then mangle it because they don't understand it? We know what, because we see it all the time. Around our shop, the joke is that "You get them all in one place and call it 'eHow.'" Don't believe us? Well, we have plenty of reasons to think so. Our latest is the mess eHow freelancer Joanne Robitaille made of some pretty basic information when she tried to explain, "What is the Purpose of a Car Transmission?" for ItStillRuns.com. We especially like her illustration, which is of a radiator...

Although her reference list got chopped when Leaf Group niched the post, Robitaille in reality did little more than condense the information in a post at someplace called "Family Car Parts." Joanne's problems, however, were many: first, her one reference was entirely about automatics, which probably explains why she doesn't mention manuals  (or CVTs) at all. Second, to be honest, she just didn't get it. Let's compare her explanation...

"Transmissions are an essential part of what makes a car run. It's attached to the engine and ensures that the engine and wheels turn in sync with each another. Think of the transmission like a chain on a bicycle. It keeps the engine (pedal) turning in time with the wheel regardless of what gear the vehicle's in..."

...with an explanation we found at well-known automotive website Edmunds.com:

"The function of any transmission is transferring engine power to the driveshaft and rear wheels (or axle halfshafts and front wheels in a front-wheel-drive vehicle). Gears inside the transmission change the vehicle's drive-wheel speed and torque in relation to engine speed and torque."

Notice those missing words "transfer" and "torque" in Robitaille's explanation, an absence we suggest might have something to do with her BA in English. Instead, we get the notion that the engine and wheels are "in sync." At least she included the "i"...

Well, Joanne, here's what happens if the wheels and engine are "in sync": based on a wheel plus tire diameter (rolling diameter) of  29 inches, an engine turning over at 2500 RPM would drive the vehicle at about 3.6 miles per minute, something like 215 MPH. To stay within the 25-MPH speed limit in a school zone, the engine would need to be turning over at 250-300 RPM, well below the idle speed of an internal combustion engine. And that doesn't even deal with torque... No, Joanne, there's a lot more to transmissions than,

"A level of precision is needed while doing this because each engine operates at its own optimum RPM (revolutions per minute) range and it's the transmission that keeps everything in balance."

Instead of explaining that multiple sets of gears with different ratios balance the engine's power (torque) against the output speed of the driveshaft (wheel speed), Robitaille performs a half-assed explanation of an automatic transmission that reads as though the mechanism has but a single set of gears (see image above). She soon posts fractured explanations of the torque converter and the computer sensor system. All this (450-plus words) and her readers still don't know the purpose of a car transmission. They also don't know that there are other types of transmissions, including manuals and CVTs. We guess that's what you deserve for using eHow (or its daughter niche sites) to search for factual information. Don't they know they're gonna get the sort of throwaway junk penned by our Dumbass of the Day?

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