Why Do Semi-Trucks Have so Many Gears?

Listening to semi-trucks take off from a stop light, you can hear the many gear shifts happening in the truck’s drivetrain. These big trucks take off slowly from a stop, and many of us will try not to be behind them because we know they can’t get up to speed in a hurry. Even so, have you ever wondered why these trucks have so many gears? Let’s find out.

How many gears do semi-trucks have?

Semi-Truck on Highway
Semi-Truck on Highway | Shutterstock

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FleetNet America tells us that standard semis have ten gears. That said, it’s common to find big rigs with 13, 15, and 18 gears. These gears, similar to the gears in your car, are necessary for the vehicle to slow down and speed up.

Why so many gears?

Most of us are used to manual-transmission vehicles with at most seven gears. It’s common to find stick-shift cars with six gears, but these 18-wheelers are taking the gears to a whole new level. The reason for the number of gears is the narrow power band for each tear. Some gears, especially the lower numbers, have less than 750 rpm between them. This is optimal when pulling heavy loads and required to keep these massive trailers under control.

How much weight does an 18-wheeler carry?

A Line of Semis Heading to the Weigh Station
A Line of Semis Heading to the Weigh Station | Shutterstock

Most semi-trucks will pull loads up to 80,000 pounds. That’s the equivalent of 25 Subaru Impreza sedans. This massive weight takes a lot of force to get it moving forward, slowing it down, stopping it, and keeping it under control. Hence, the large number of gears in the transmission of a semi.

How much does an 18-wheeler cost?

A used semi-truck typically costs between $45,000 and $100,000 with a new model priced between $125,000 and $150,000. Forget that Ferrari; buy a semi. Some truckers buy their trucks and work independently, which allows them to pocket the entire payment from each trip. These independent truckers must pay higher up-front costs to own their trucks.

How many miles can a semi-truck drive on a full tank?

Semi Straddling the Yellow Line
Semi Straddling the Yellow Line | Shutterstock

18-wheelers equipped with two tanks can typically drive for 2,100 miles between fill-ups. Each tank holds approximately 150 gallons of diesel fuel, and many semi-trucks average 7 miles per gallon. Some trucks only have one tank, which cuts the distance in half.

How long do semi engines last?

Many of us might look at 100,000 miles as a threshold to look for a new vehicle. This is when semi-trucks are just getting started. Many semis can drive for up to 720,000 miles when properly maintained. It’s not uncommon for an 18-wheeler to reach over one million miles, especially if the truck is well cared for throughout its lifetime.

Why do truckers flash their lights when you pass them?

Semi-Trucks in Traffic
Semi-Trucks in Traffic | Shutterstock

Typically, trucks flash their lights when you pass them and signal that you want to get into the lane in front of them. This is to inform you that there’s room for you to change lanes and safely move in front of their semi.

Now you know a little more about the big rigs that share the road with you. These trucks are the heartbeat of our transportation system. Most retail store shelves would be empty without semi-trucks and the men and women driving them.

Next, check out some of the worst SUVs in history, or watch an explanation of the many gears of semi-trucks in the video below:

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