What Is Overdrive?

What Is Overdrive?

Last Updated February 5, 2020 | Sam Padgett

Overdrive: It’s one of the cooler-sounding features of a car. It either evokes images of a loud, screeching guitar, that weird Stephen King movie where cars come alive, or simply driving over the speed limit. In reality, overdrive isn’t really that exciting. Instead of helping your car go fast (while it does do that, in a way), it’s more of a preventative measure, a way to take the strain off both your engine and your gas tank. Mustangs do come equipped with an overdrive gear, so if you are wondering what it is, when it should be used, and when it shouldn’t, we’ve got the answers that you need.

What Is Overdrive?

White Shift Knob

Overdrive is simply a set of gears. Unlike the lower gears where the gear ratio is above one, overdrive is a gear somewhere between 0.6 to 0.8:1. This means that the wheels of the vehicle will rotate more per single-engine rotation, allowing the engine RPM to remain low, while the speed remains high. As opposed to the first few gears, where the ratio is greater than one, overdrive gears are more focused on rotation speed rather than torque. In fact, overdrive gears provide less torque to the wheels than other gears. The opposite of an overdrive gear is a granny gear, a gear that provides a ton of torque to the wheels but barely any speed. You'll see this type of gear more on classic trucks than on Mustangs, however.

When Should You Use Overdrive?

Overdrive should really only be used when traveling at high speed for a long time. Basically, this gearing came about around the proliferation of America’s expansive highway system. Now that it’s basically a given that if you commute, you will have to be on the highway at some point or another, overdrive helps preserve the engine and, consequently, fuel.

When Shouldn’t You Use Overdrive?

You shouldn’t really ever use overdrive whenever you are driving in any situation that requires high torque. Even if you are traveling consistently at high speeds, overdrive can be a hindrance on steep hills, or in situations in which you are trying to pass another vehicle. Basically, overdrive should only be used for cruising, because that’s where it can truly help preserve both your engine and limit your fuel consumption.

Overdrive on a Manual vs. an Automatic

Automatic Shifter

The overdrive gear, as should be expected, operates exactly the same on both manual and automatic cars. After all, it is just a gear with a low ratio. The only real difference between the two cases is essentially the main difference between a manual and an automatic in the first place: On a manual, you have to decide when to engage overdrive as opposed to the transmission selecting it for you. Some automatic vehicles do have separate buttons to enable or disable the overdrive gear, but the vehicle’s internal computer still decides specifically when to engage it. On manual vehicles, the highest available gears are generally the overdrive gears. For example, fifth gear on a Mustang is the overdrive gear. While the specific gearing does change from vehicle to vehicle, the highest gear available will most likely be your overdrive option.

Overdrive really isn’t that exciting at all. It’s just as exciting as getting your oil changed and your tires rotated. Regardless, it’s still a good idea to know how this part of your car works and know best when to apply it. If overdrive is prudently applied, it can ultimately save you a lot of money in repairs and gasoline. Here at CJ Pony Parts, we know that a happy car means a happy driver.

What Is Overdrive?

Overdrive sounds much cooler than it is. What sounds like a hyper-speed option is, in reality, a quite conservative gearing for highway cruising. Whether you drive an automatic or a manual, learning when to use overdrive can help keep your Mustang running longer.

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