What Is A Bull Gear On A Semi Truck? (Everything To know)

For those who are just starting to learn about Semi Truck, they have a lot of questions related to truck parts. One of the most common questions regarding bull gear. What is bull gear on a Semi Truck? How does it work and how does it work? Why does a truck need bull gear?

To answer all of the above questions, let’s find out in detail about the structure, functions, tasks, maintenance, and how to maintain the life of a bull gear on a Semi truck.

What Is A Bull Gear On A Semi Truck?

A bull gear is an integral part of a pickup engine’s gear transmission. The task of a bull gear is to drive all gear-driven engine accessories such as the compressor, fuel pump, water pump, power steering pump, and generator. Meanwhile, a bull gear is driven by crankshaft gears.

In terms of form, bull gear is a large and heavy gear. It appears in the design of large vehicles such as pickup trucks. The job of a bull gear is to power the engine to move the wheels of the car and move the car to move forward. You can easily find bull gear on pickup trucks or some other heavy vehicles like buses, dump trucks, and tank trucks.

Materials for creating a bull gear are usually extremely strong and durable materials such as steel or iron. This ensures that a bull gear can withstand great pressure during operation.

The shape of a bull gear usually looks like two interlocking circles with toothed blades along its circumference. These blades play an important role in allowing gears to rotate and transfer force between two different axes as vehicles move.

The size and shape of a bull gear will vary depending on its application. However, versions with larger sizes are often used for heavy vehicles such as tank trucks, dump trucks, and buses. Besides, the external power source to connect to a bull gear is usually a diesel engine or an electric motor.

How Does Bull Gear Work?

A bull gear on a Semi Truck is usually located under the cam, above the crank, and between the engine and transmission. Specifically, it is usually located between the above parts. A bull gear can be designed in front of the engine such as in the Detroit 60 series, while the Volvo D13 has a bull gear in the rear of the engine.

A bull gear is located at the center of the gears. It is connected to the camshaft, auxiliary transmission gear, and rotating gear and rotates the crawler gear. The air compressor and power steering are connected, and all run on bull gears. You should have your bull gear’s bearings checked annually if you notice strange noises. However, knocking can also be heard when the engine is on the compressor. Annual maintenance and inspection are vital to maintaining the life of your truck and keeping it working efficiently.

What Are The benefits Of A Bull Gear?

Bull gear will bring many benefits to the vehicles using them and ensure high-intensity operation. Some of the benefits you may notice are:

  • Firstly, bull gear is extremely reliable thanks to durable and strong materials like steel and iron. Therefore, it can withstand high pressure without breaking down or wearing out quickly.
  • Second, it effectively ensures the transfer of power from an external source (such as a diesel engine) directly to the wheels and propels it forward without any problems.
  • Finally, a bull gear can maintain power and keep the vehicle running at high pressures with low maintenance or repair costs.

Do All Semi Trucks Have Bull Gear?

The answer is NO!

Not all pickup trucks have bull gear. Some models have a bull gear like Detroit 60 (12.7L and 14L), Cummins ISX engine, and Volvo D13 engine. DD15, DD13, and DD16 have no bull gear.

Most pickup trucks that have a gearbox and two gears that mesh together to promote movement will have bull gear. In addition, manual transmission pickups will also have a bull gear.

The crawler gear is a key component in the gear system and will require periodic maintenance. In addition, you need to learn a lot of information about the engine to detect abnormalities in time and handle the situation effectively.

Some Common Problems Related To A Bull Gear

If a bull gear on a pickup truck has a serious problem, it will affect the oil pump to the engine. When a bull gear has a problem, it will vibrate when the vehicle moves. It will rub against the inner housing and other connecting parts such as the air compressor and the drive gear. From there, the whole system will work abnormally and make strange sounds when the pickup is operating.

A broken bull gear is when it doesn’t stay in place and slips out of connections with other components. It will deviate from the design center and cause other operations to be changed. This will cause excessive friction between the bull gear and other gears in the system. The gears can become excessively worn and allow the metal to enter the engine.

A noise will be generated when a bull gear is malfunctioning. The noise level will increase more sharply as you accelerate the truck. You can also check the condition of the other gears it drives, such as the compressor gear. If the pneumatic gear is damaged, it will seriously affect the bull gear.

When Should You Service A Bull Gear On A Truck?

The blades on a bull gear will have to work continuously when the car moves by sliding over each other. Therefore, it will create a huge pressure on the teeth and can lead to shape deformation if operated for a long time.

These tooth blades may become excessively worn, break, or fail to engage with other blades as the engine rotates. Too much pressure will also affect the entire engine if you do not repair it in time.

The best way to protect a bull gear and the engine is with regular, periodic maintenance. Regular maintenance will ensure that a bull gear is lubricated regularly and the oil is maintained at a safe level. In particular, you should change a bull gear when the car has traveled 750,000 miles.

How To Prolong The Life Of A Bull Gear On A Semi Truck?

One of the key things to help prolong the life of a bull gear on a truck is to use good quality oil from the manufacturer. Cheap and poor-quality oil will cause a bull gear to lose its life faster. In addition, the friction between the gears is extremely large, so it will generate a large amount of heat. Therefore, you should use the right oil consistency that will prolong the life of your bull gears.

You should regularly check the alignment between the gears with a raised bar. You should also pay attention to strange sounds from the engine and find the cause as soon as possible to fix it.

In addition, proper use of the vehicle, protection of the vehicle and compliance with the manufacturer’s regulations, regular and regular maintenance will also help increase the life of a bull gear because they are all combined. connected in a unified whole. In particular, regular maintenance and maintenance is extremely important for other parts of the engine.

You should also not carry more than the weight specified by the manufacturer because it will put a lot of pressure on the engine and cause them to wear out quickly. The cost for you to change the bull gear will average from $1100 to $1500. Bearings range in price from $80 to $90. The total cost to replace a bull gear is between $2500 and $20,000 if your engine has serious problems. Regular engine maintenance and inspection are extremely important because it will cost you a lot of money to replace engine-related problems.


Bull gear is a large, heavy gear commonly found on large vehicles such as pickup trucks, tank trucks, dump trucks, and buses. It supplies power from an external source directly to the wheels so that they spin and propel the car forward.

Bull gear is usually made from strong and durable materials such as steel, and iron to operate under high intensity. If it breaks or crashes, weird sounds will sound and you must fix this problem quickly. If you don’t deal with this situation soon, other parts of the engine can have problems.

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