How Many Gears Does A Semi Truck Have?

how many gears in a semi truck

How Many Gears Does A Semi Truck Have?

You might be wondering how many gears a semi-truck has because of its massive performance. When you look at truck driver take off, you will hear the gear shifts as they’re being switched in the truck.

We know these semi-trucks of taking off smoothly and their stopping is also swift as they have to throttle down the gears before they can finally come to a stop. So, have you wondered how many gears a truck has? Then I will be happy sharing the idea with you on this epic article.

How many gears do semi-trucks have?

The number of gears an 18-wheeler may have is between nine and 18 gears.

The most common set-up for a semi is two reverse gears and ten forward gears, or 12 total. Ultimately, the engine determines the number of gears in the transmission. More gears, or a range of gears and split gears, can help a driver and truck navigate safely with minimal stress on the transmission due to needing higher RPMs.

It’s unusual to find a truck with 18 gears. These are typically used to precisely control power in situations where you’re towing an extremely heavy load through variable terrain. You should receive training in using this complex manual transmission if you choose to pursue a career in trucking.

FleetNet America reports that standard semi-truck has ten gears. Even the big trucker’s gears range from 13 gears to 18 which help them perform at their best at any scenario. The gears are similar to the gears in your little car. Just as you switch gears while driving, climbing a hill, or taken off from a stop state, and speeding.

Why so many gears?

You may ask the question the reason behind the almost a dozen gears. I can answer this with the knowledge we have had with manual-transmission vehicles that comes with seven gears. We have seen cars with just six gears and with that, we drive them at our best. Likewise, the truck that comes with 10 to 18 gears.

The gears are there to help narrow the power band for each tear. Some lower gears in the truck has less than 750 rpm between them. This is useful when they take on heavy loads and will be able to keep the truck in check and effective mobility.


This is another reason why trucks come with many gears. With the more gears, the truck engine always works in economic speed range. When a trucker wants to speed up or slow down, the so many gears adjusts effectively between tears and help for smooth transition of each phase. Just like reducing the engine speed, move in gear shifts swiftly, and also save fuel.

With many gears, a semi-truck can minimize fuel consumption when it drives in a mountainous road. In a long mountainous road, 3 gears waste too much and the engine power is not enough to propel the car at 4 gears. Furthermore, the truck fuel might not transmit effectively and run smoothly at 5 gears. That’s why the truck is equipped with many gears to help it in such scenarios.

More gears also increase the truck speed range.


The many gears in truck helps for smooth gear shifting between two near gears. Depending on the speed limit the trucker is driving, he can adjust smoothly his gears to match the truck’s load and its weight. Also, it’s easier and faster to control the truck engine performing speed and power.

The many gears help the truck perform at its best just as our little car can do with 7 or 6 gears. It also increases fuel economy, dynamic performance, and driving operability.

18-speed transmissions are laid out in an ‘H’ pattern. The driver shifts from the second to the fifth gear as you would for a normal sedan then split up the gear into the high range. Then, shifts again from the sixth to the ninth gear. From the ninth gear, the driver splits up to overdrive for the top gear.

There are lots of gears in between since all the main gears have a high and low range with different RPMs. However, their power band is very narrow, and the difference in revolutions between the gears is often less than 750 RPM. So, as the driver, you can split these gears as necessary. As the driver practices and gains more experience driving semis, he will realize that the gear being used may not be the right one for where he wants the RPMs to be.

Here, he will shift up or down as needed to match the RPMs to the sweet spot of the engine. This is another reason semi-trucks have so many gears; to select the right RPM depending on the speed of the truck.

However, since trucks produce a lot of torque, it becomes more difficult to bring them to a stop using the brakes only. Thus, you need to downshift the truck to lower its momentum before finally bringing it to a stop.

That is why you need to reduce its speed by downshifting to a comfortable speed before applying the brakes. Otherwise, you will destroy the brake pads, clutch, and many other components in your truck.

Applying Gears in Semi-Truck

Truckers will not always use the gear when driving. There are scenarios that call for usage of number of gears. Truckers sometimes will ‘block shift’ or skip gears to elongate the life span of the gearbox and prevent wear and tear.

For instance, if a truck has 12 gears compartments, it’s not going to use the first gear to start if its carrying heavy load and it’s about to drive an uphill, or they need to maneuver the road. And certainly, they won’t need to use the remaining 11 gears while switching gears or slowing to a stop.

In a truck that runs with six-speed, truckers start in second gear; while in 12-speed truck, truckers likely start with the third or fourth gear if the truck is empty or use the second gear if the trucker is to pull a load.

Also, starting a truck with its higher gear is smoother to move than the lower gears. Because it reduces the chances of its wheels to spin because it has less rotational force.

Unless the truck is an automatic gearbox, the trucker can smoothly change gears by paying attention to the revs and observation from the trucks performance if its striving or if the rev range is increasing and may need to be reduced to prevent engine damage.

About Daves 41 Articles
David Samuel is an accountant and Tech-Savvy. He is the author of Art of Public Speaking available on Amazon KDP. Blogging is part of his hubby as he likes sharing ideas with his huge fan base on Facebook and Twitter.

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