How Does a PTO Work on a Truck?

Power take-off units (PTOs) allow trucks to perform the functions they’re designed to do. PTO pumps for semi-trucks are mounted and use power generated by the engine to power auxiliary equipment. They also simultaneously operate the truck’s body without needing another power source. Continue reading this article to learn more about how a PTO works on a truck and its applications.

Understanding Power Take-Off Units

PTO pumps for semi-trucks have three main types—transmission, flywheel, and full-power. Choosing a suitable power take-off unit for your applications is critical. While the PTO may be a single component of the many working parts of your fleet, it is one of the most important elements of successful operations.

Flywheel PTOs

This type of PTO works on a truck by directly attaching to the engine. This allows the power take-off unit to perform while your vehicle is stopped or running. Trucks that require continual rotation, like cement trucks and refrigerated trucks that must maintain and adjust the temperature, commonly utilize flywheel PTOs.

Transmission PTOs

Transmission PTOs connect to the side or bottom of a truck’s transmission. Because of ease of installation, versatility, and cost-effectiveness, transmission PTOs are the most commonly installed. The main factor that sets these power take-off units apart from others is that they can only be put to use when your vehicle is stopped. This makes it possible to power cranes and aerial work platforms via a truck’s transmission.

Full-Power PTOs

When you need to generate as much power as possible from your truck engine, full-power PTOs are the ideal solution. They’re installed between the engine and transmission, allowing power transfer generated by the engine to the auxiliary unit while a truck is stopped. You’re most likely to need this type of power take-off unit on dump trucks and other vehicles that require a robust power source to handle heavy workloads.

What Role Does the Power Take-Off Shaft Play?

Your PTO works on a truck by efficiently transferring power from the driveline to another application. Typically, this is done by transferring power to the secondary application, like hydraulic pumps, pneumatic blowers, vacuum pumps, and air compressors, through the power take-off shaft.

Power take-off shafts are required for power take-off units that transform engine energy into hydraulic pressure. Because they take on substantial workloads, PTO shafts require routine maintenance to avoid damage and deteriorating the quality at which a PTO works on a truck.

If you need a power take-off unit for your truck, reach out to White Tank & Truck Repair. We have over four decades of experience installing, repairing, and maintaining equipment so your PTO works on a truck when needed.

The Difference Between Hydraulic and Mechanical Power Take-Off Units

When it comes to independent PTOs, there are two main types, mechanical and hydraulic. Hydraulic shift PTOs work on a truck by engaging through the use of a clutch mechanism. They apply to the torque converter, also called traditional automatic transmission.

A mechanical shift PTO is engaged by physically shifting one gear into another. This process is completed by using a lever, cable, or air pressure in most circumstances. These can be used as an application for automated and manual transmissions.

How To Determine Which PTO Works on a Truck In your Fleet

Determining the technical specifications to choose the right power take-off unit for your truck requires knowing the technical requirements of your application. PTOs must correspond with the transmission they’re being attached to. That’s because transmissions have a particular opening and drive gear.

One thing that makes choosing a PTO difficult is that several configurations can work for an application, but they might not meet your objectives. Take, for example, fuel efficiency. With today’s rising fuel prices, fleet managers are paying closer attention to consumption. Just because a PTO works on a truck doesn’t mean it can optimize efficiency.

Below are simple formulas the trucking industry uses to calculate what is needed from their PTO equipment for specific applications:

Pump Out Horsepower

Horsepower (HP) = Gallons per minute (GPM) x pounds per square inch (PSI) ÷ 1714

Pump Input Horsepower

GPM x PSI ÷ 1714 ÷ efficiency

Pump Input Torque

Cubic inches displacement (CID) x PSI ÷ 75.36

Gallons per Minute

CID x revolutions per minute (RPM) ÷ 231

Cubic Inches Displacement

GPM x 231 ÷ R.P.M.


Torque (T) x R.P.M. ÷ 5252

Flow in GPM using PTO

Engine R.P.M. x P.T.O. % x CID ÷ 231 x E

CCM Conversion

CID x 16.39

CID Conversion

CCM x .06102

Power Take-Off Unit Maintenance Needs

To ensure a PTO works on a truck, providing it with regular maintenance is critical. Preventative maintenance ensures the smooth and safe operation of your PTO system. Before each day’s use, examine all air, mechanical, hydraulic, and other PTO-driven mechanisms, like universal joints and power take-off shafts, before operating your equipment.

At the beginning of each month, your team should inspect for leaks, tighten all mounting hardware, torque nuts and bolts to the manufacturer’s recommendations, and make sure splines are sufficiently lubricated.

White Tank & Truck Repair Is Your Source for All Power Take-Off Unit Needs

For nearly 40 years, White Tank & Truck Repair has been Missouri, Kansas, and southern Illinois’s one-stop shop for the trucking industry. Our award-winning and certified team of experts have vast hands-on experience installing and servicing everything from power take-off shafts to entire PTO systems.

We know each minute you’re off the road and in the shop is money out of your pocket. That’s why we work efficiently without ever compromising on quality. White Tank also keeps a large inventory of parts and accessories on hand so you don’t have to wait for vital pieces to arrive. If you want to make sure your PTO works on a truck in your fleet, reach out to White Tank today.