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Why do some cars have more gears than others?

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Updated 11 Oct 2019

Jason Unrau

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Car shopping is often fun and exhilarating, checking out awesome new vehicles and going for test drives.

But it’s also exhausting.

How are you supposed to know what all the specs mean?

Take for example a transmission.

One car you’ve seen has a four-speed transmission while another has a six-speed.

You’ve even driven in a sports car with a ten-speed automatic transmission.

What’s all the fuss about?

Why do some cars have more transmission gears than others?

Here’s a look at three reasons that manufacturers make transmissions with different numbers of gears.

Smoother shifting

One of the most popular reasons for making an automatic transmission with more gears is for smoother acceleration and deceleration.

When there are more gears in the transmission, closer gear ratios can be used.

For the driver, that means the engine RPMs don’t vary as much when speeding up and slowing.

You feel the shifts less as the transmission goes through its gears.

Higher top speed

Another great benefit for having a transmission with more gears is the ability to include additional overdrive gears.

Overdrive means the transmission output shaft is turning faster than the input shaft.

The engine speed will be lower to achieve the same wheel speed.

The benefit? You can go faster with the engine revving up less.

This is the case with the new 2018 Ford Mustang’s 10R80 automatic transmission.

It’s available with a triple-overdrive automatic transmission to allow for ridiculous top-end speed.

Better fuel economy

Something that everyone appreciates is skipping a petrol fill-up.

A transmission with more gears typically reduces fuel consumption.

No, it’s not magic.

Take a common four-speed overdrive automatic transmission for example.

Before it changes gears, it revs up to about 3,000 to 3,300 RPM on light acceleration, then starts the next gear at around 1,500 RPM.

And while driving at highway speed, it holds steady at about 1,800 RPM.

Comparatively, a six-speed automatic transmission revs to about 2,500 to 2,800 RPM on light acceleration and drops down to 1,500 RPM for the next gear.

At highway speeds, a second overdrive gear allows for lower cruising RPMs of 1,600.

All in all, there’s less engine load, and lower engine RPMs.

The less an engine has to work, the less fuel it burns – simple as that.

Are there any negatives to more gears?

Having a car with more gears is mostly just an upside.

There are two factors that you can consider negatives though.

A transmission with more gears can cost more for your initial investment.

You’ll spend more money to buy a car with the extra gears because it’s better technology, more fuel efficient, and a popular choice.

Comparatively, it’s more expensive to fix.

For example, if you have problems with an eight-speed transmission, it will cost more to repair than a five-speed transmission.

There are more moving parts, extra seals and clutches, and probably more labour time to complete the repair.

No matter whether your car has 4 gears, 5 gears or 10 gears; a qualified mechanic on AutoGuru can help with all your transmission needs!

Get quick quotes and book online!

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Written By

Jason Unrau

Jason is a Canadian automotive content writer with a background in the auto service industry, but he’s been hooked on cars and mechanics since childhood.

One of his first cars was an ’80 Mazda RX-7 that’s sorely missed to this day. A ’68 Ford Torino GT, a ’66 Ford Country Squire Woodie station wagon, and a ’96 Suzuki GSX-R 750 have spent time in his fleet of cars, bikes, and trucks over the past two decades.

Jason’s pride and joy is under construction – a turbocharged ’88 Mazda RX-7 convertible. Also on his resume is CASCAR official certification.