HOW TO SPEC A PTO (Power Take Off)
By: Parts for Trucks
Choosing a PTO (Power Take Off) that works with both your truck and application can be a complex and confusing process. An incorrect PTO can damage equipment and tie your trucks up in the shop while you wait for repairs.
There are 7 main considerations when choosing the correct PTO system:
Consideration #1 – Transmission
The first and most important step in choosing the right PTO is identifying the make and model of the trucks transmission. The transmission dictates what you can install based on the sizes of openings and the RPM you can expect. The location of the transmission opening can also dictate the type of PTO you will be able to install. If you are having issues identifying your transmission, consider calling your truck dealer, they may be able to identify the transmission based on the VIN.
Consideration #2 – Driven Equipment
So, you know what transmission you have and where a PTO is going to fit, great! Next is to match your equipment to the output RMP, improperly matching your output RPM with the required RPM of your equipment can lead to equipment that doesn’t work. In the case of pumps, which we frequently see, a fixed horsepower is required to produce and maintain a proper flow of fluid. How do we know the horsepower coming from your system? A simple equation:
Hydraulic Horsepower = Flow (GPM) x Pressure / 1714
If the HP required by the equipment is higher than the horsepower capability of the system, you will damage the system.
Consideration #3 – Engine Speed
Engine speed is a relationship between the RPM of the PTO and the RPM on the engine. You want to make sure you can achieve the necessary RPM for the equipment while maintaining a comfortable RPM on the truck engine. The PTO’s speed is represented as a percentage of the desired engine speed while the equipment is being used. For a hydraulic pump, an engine speed of 900 to 1200 RPM is common.
Remember PTO speed is represented as a percentage so if you are calculating this on your own, it will return a decimal such as 0.73 which is equal to 73%. If your answer includes a 1 ahead of the decimal point, it means you are running greater than 100% of engine speed. For example, 1.36 = 136%.
Consideration #4 – Rotation
If you don’t want to rip the gears apart in your equipment and truck, you’ll want to pay attention to this section. A lot of people get this one wrong, your equipment or hydraulic pump will either require a clockwise rotation or a counterclockwise rotation. The common misconception is that clockwise equipment gears need a clockwise geared PTO, but that is incorrect, this is because they are spec’d from different perspectives. When you are designing your system and get to this step, position yourself where the driveshaft would go. “Look” at your PTO, you would see it spinning the driveshaft clockwise, but when you turn your head to look at the other end of the drive shaft, you will see that it is spinning counterclockwise.
Think back to your days in the schoolyard when you were the 4th grade skip rope champion. When you’re jumping a rope and look at one end the rope will be rotating clockwise, look at the other end, and you’ll see it rotating counterclockwise. The rope as a whole, is rotating the same direction, but from your perspective, it is different at both ends.
When you’re building your system, make sure the PTO matches the equipment, if you’re retrofitting and it doesn’t match, that is okay, you can purchase an adapter for most PTOs that will change the output rotation.
Consideration #5 – Connection
This one is a simple one, how are you connecting your equipment to your PTO? Is it direct drive? Or do you need at driveshaft? If you need a driveshaft, you’ll need to spec something in accordance with your system.
Consideration #5 – Use type?
How often will the equipment be used? Intermittent or continuous1? If you are running a continuous system, you will need to adjust the amount of torque in the system, otherwise you will damage your PTO and shorten its lifespan. To calculate the appropriate torque for a continuous system, use this equation:
Continuous System Torque = 0.7 x (horsepower x 5,252 / PTO output RPM)
Consideration #6 – Reverse?
Does the system need to go in reverse? No problem if it does, it just requires some different equipment to get the job done.
Consideration #7 – Engagement system.
How do you want your system to be engaged? There are several ways to achieve this, it all depends on how you plan to use your system and what works for your truck.
Retrofitting your system
If you are retrofitting your system, you can easily identify the PTO and its configuration by its serial number. Reference the manufactures website to see what PTO you have on your truck, and you’ll be able to build a system accordingly.
With the help of a Parts for Trucks representative, we can ensure your PTO is properly spec’d for your application. A properly spec’d system with regular preventative maintenance will last almost as long as your truck and have very little down time during its life.
If you’d like to know more or are ready to purchase your system, contact one of our locations either in person or by phone and we will be happy to build a custom system that fits your needs. We can even install it for you at any of our service centers across Eastern Canada.
1 – it is considered a continuous use system if it runs for 5 minutes or more every 15 minutes.