Cutting A PTO Shaft

Why does one need to shorten a PTO shaft? If a PTO shaft is to long then it can potentially damage the gear box on the implement and in turn damage the seals & bearings in the PTO on the tractor. This may happen when you pick up the implement which retracts the shaft into the fully closed position. If the shaft is to long then it can get pushed into either the gearbox input shaft seal & bearing or the seal & bearing on your tractor PTO. The wrong length shaft could end up costing you a lot of money and time.
When you get a new PTO shaft compare it to your old one to be sure the length is right in the fully closed position. If the length is the same then all is good, if not, then here is what you will want to do. The first thing you will need to do is to determine how much you will need to shorten the new shaft. If you still have the old shaft and it can be measured then use it as your guide & skip this measuring section and go straight to the cutting directions. It will be simpler if you have your tractor, the implement, and the PTO shaft in one place so we can get some measurements. Here are the tools you will need to do this: a yardstick/level or some sort of straight edge, a tape ruler, a marker, hacksaw (or some sort of saw that will cut metal & plastic), a file, and a box of paper towels/rags. The first measurement you will need to take will go from the notch on the input shaft on the gearbox to the center line on the lift arms pins on the implement. The 2nd measurement will be from the end of the tractor output PTO to the center line on the lift arm balls. Once you have these 2 measurements add them together for the total length of the shaft at its longest needed length. Then you will need to subtract 2 - 3” to make sure it won’t bottom out. If you are not confident or just want to verify these lengths are correct pull the shaft apart and lay them side by side. Then deduct the amount that you have measured and figured you need to cut off and lay it out with the new dimensions. It is always better to measure twice before you make cuts and this is just another way of measuring twice.
To give a concrete example of this, let’s use a PTO shaft (ASC# 35734) for a smooth shaft that is often used for a rotary mower. Fully closed it is 37.8” in length from the end of one yoke to the other yoke. When we measure from the tractor PTO to the center line of the lift arm balls is 22” (for example) and from the attachment point on the input shaft on the mower to the mid-line point of the lift arm pins is 10” (for example). Then that gives us a total length of 32” that our PTO shaft should be when it is installed. The shaft we have is 37.8” and when we subtract one from the other we get 5.8”. When we add the extra 2” so it doesn’t bottom out against the gearbox/tractor PTO we will need to cut 7.8” leaving us w/a 30” fully closed shaft.
Now to cut the shaft we will pull it apart to cut even amounts off both ends. We will cut 7.8” off both sides which will leave us w/the 30” fully closed shaft. To make this easier to reassemble we will cut the plastic sleeves 8.8” which will allow us to see the ends clearly when we put it back together again. You can cut the metal tubing w/either a metal cutting band saw, a hack saw, saws all, or whatever works best for you to cut metal. Once you have made your cuts you will take a metal file and file off any burrs you may on the cut ends. Then take some grease to put along the flat surface of the metal tubing to allow the tubing to slide smoothly along each other when it is reassembled. Now you will see why you cut that extra inch off the plastic sleeve, you can see the two ends of the metal shafting to slide it together. You are now ready to connect the PTO to your tractor and mower.