Find the Right PTO Shaft

The appropriate PTO shaft is essential for ensuring a smooth and seamless transfer of power between a tractor and an attached implement or machine. Size is a crucial consideration when choosing a shaft, as is the PTO driveline series.

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If you make a mistake or measure incorrectly, you will likely cause damage to the shaft, tractor or implement — or all three. Furthermore, you may need to replace the PTO shaft tubing, U-joints, yokes or other shaft components.

If you’re in the market for PTO shafts or parts, you’ll find no shortage of options. Finding the right PTO shaft for your equipment can be challenging with so many choices, but PaulB Parts makes finding the right PTO shaft easy. This article offers advice on choosing proper PTO parts that will work with your equipment. We also provide extensive resources so you can determine what you need and offer the guided support of our knowledgeable staff.

PTO Shaft Selection Tips

Determining the correct PTO shaft that will function properly with your tractor is crucial to the maintenance and effectiveness of your equipment. Follow this advice to find just what you need the first time.

1. Determine if Your Driveline is North American

The first step in deciding which PTO driveline you need is figuring out if your PTO is North American or metric. You can easily determine this by the shape of your driveline’s tubing. Look at the shape of the tubing on your driveline. North American PTO drivelines are typically one of four shapes: square, round, rectangle, or splined.

On the other hand, a driveline shaped like a lemon, star, or with three lobes is likely metric. Specifically, lemon and star profiles typically belong to a German series PTO shaft. A tri-lobe profile indicates it is an Italian series shaft.

2. Take Appropriate Measurements

Next, take two measurements from the U-joint that is on the tractor or the drive end of the PTO:

• Measure the bearing cap diameter: Most U-joints have uniform cap diameters. Cap diameters can differ among Constant Velocity drivelines. For best practice and further accuracy, measure all caps.

• Measure the cross-kit width, cap to cap length: You will also need to measure the U-joint from the end of the cap to the end of the cap. To get the most accurate reading and increase your likelihood of finding the right PTO shaft, remove the cross-kit from the yokes before measuring.

Keep in mind the fact that some series are not uniform in width. Measuring the cross kit both ways is the best practice to ensure accuracy.

3. Look at Your Existing Equipment for Specifications

Locate the snap ring. If it’s in the bushing, it’s an internal snap ring. If not, it’s likely in the yoke ears and is an external snap ring. Note the bearing diameter, cap-to-cap overall length and snap ring type. It’s also important to know the amount of torque and horsepower needed to move through your PTO shaft. Male and female parts should have at least 6 inches overlap for torque load. Check the owner’s manual if you are unsure.

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One of the key factors in getting quality equipment is knowing how to take care of your existing equipment. When your equipment is not in use and is stored outside, take the PTO shaft off the machine, tractor or mower and keep it inside to avoid rust-causing moisture and prolong the life of your driveline.

Get a PTO Shaft that Works with Your Tractor

You need to consider several factors when purchasing a PTO shaft, and after you buy, you may find that you need to make a few adjustments so the shaft is the perfect size for your tractor. For example, you may need to cut your driveline to the proper length for operational overlap. If you raise your implement to get the shaft on, you could end up damaging your equipment. You should have an overlap of at least one-third between the shaft and tube. With a slip-sleeve, there will be about 3 inches of overlap.

If you need to shorten the shaft, check out our tips on cutting your shaft to size. We want to make this process easy for you by providing online resources and offering access to our team’s experienced knowledge by phone so you feel confident in the parts you buy. PaulB Hardware can help you find the PTO driveline you need! Browse our selection of PTO shaft drivelines online to find all the parts you need.

Research PTO Shaft Details Before Making the Final Purchase

PaulB Hardware provides a variety of resources to make your shopping experience more effective. We offer videos, articles and diagrams to help you understand the details of the parts you are purchasing. Our website has content that will help you with the following:

• Figure out the proper PTO series: We offer a thorough step-by-step process for determining your PTO Series through careful measurements. We’ve even included a handy tool to make the sizing process even easier!

• Taking apart a universal joint replacement: PaulB Hardware provides a comprehensive guide that tells you how to take apart a universal joint replacement, complete with pictures and detailed captions.

• Choosing between a Weasler E kit and a Weasler R kit: We know the importance of getting the right product the first time. That’s why we have a video detailing the difference between Weasler E kits and Weasler R kits to help you decide which one is right for you.

Another thing, that I had forgotten, and will write a treatise with bad MS Paint images if need be, is that if you have three U joints, you need to treat them as two separate driveshafts, since the driveshafts will be 90 degrees out of phase with each other.

So you will measure the angle of the trans to the front driveshaft, which needs to be the same as the angle from the front driveshaft to the rear (sign does not matter).  Then the angle of the front driveshaft to the rear driveshaft needs to be the same as the angle from the rear driveshaft to the differential (again, sign does not matter).

So if you had 2deg in the front and 2deg in the back and 0deg in the middle, it won't be right.    You'd need to raise or lower the center bearing, and then adjust the diff angle.  

As I implied before, it can be "fun".

If you had to make a choice, it is best for the longer driveshaft to have the lowest angles. 

Having angle in the joint causes the driveshaft to speed up and slow down twice per revolution, more angle causes more speed variance.  This is why you have to clock the U joints, and why you want equal angles at both ends, so the speed change cancels out.

Some people hate them, but I really like double Cardan joints, they eliminate all this fuss

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