PTO Shaft Maintenance – Don’t Neglect This!

Regular maintenance of your PTO shafts is essential to ensuring reliable and safe operation – AND ensuring your safety as well! In this post, I cover how I maintain my two PTO shafts, which happen to be two of the most common PTO shaft designs.

The ends of the PTO shafts shown below connect to the tractor PTO and have universal joints to allow them to operate at a range of angles from the PTO. The one on the left is the PTO shaft for my brush hog and the one on the right is for my wood chipper.

The couplers on each are two of the most common kinds you’ll likely see.  The brush hog PTO shaft has a slip collar that releases when the collar is pulled back and the wood chipper PTO uses a spring-loaded release pin.

I start the maintenance by wiping dirt and grease off the universal joint grease zerks, Next, I give each several squirts until I see fresh grease oozing from the joints.  This should done before you use the PTO shaft and after every eight hours of operation. Then I wipe the excess grease and as much dirt as I can get to.  There’s a little more to do on this end which you’ll see later in the post.

The other ends of the PTO shafts connect to the implement and they have perhaps the two most common shear pin designs.  Starting with the brush hog shaft, the shear pin is a half inch by 3.5” long, grade 2 bolt with a nylock nut on the end.  BTW, most shear pins are grade 2 bolts so that they are soft enough to shear when needed.  Any higher grade than 2 would be too hard and your tractors PTO won’t be protected from the shock of hitting a large rock or stump with your brush hog, possibly causing serious damage.  The coupler is smooth as is the shaft on the brush hog gearbox.  The shear bolt runs through the implement shaft to mechanically couple the PTO and implement together.

There is a grease zerk that lubricates the coupler and implement shaft so that if the shear pin does shear, the coupler can spin freely on the implement shaft.  There is also a grease zerk on the back side of the universal joint, which is accessible when the protective shroud is disconnected and pulled back.

Finally, there is a snap ring that goes on the end of the bush hog gear box shaft, which keeps the coupler from backing off the shaft if the shear bolt shears.  However, the gear box safety shroud makes it almost impossible to put the ring on and take it off.  The shroud also makes it had just to connect and disconnect the PTO shaft from the bush hog, making it next to impossible to change the shear pin in the field.  This is the major drawback of this shear pin design.  To get around it, I’m going to replace the gearbox shroud with one that I build that will make it easy to service the PTO shaft.  That will be covered in another upcoming video and post.

As shown in the picture below, the wood chipper PTO shaft has a 5/16” x 2.5” grade 2 bolt for the shear pin, which transfers rotational power from the universal joint to the six spline coupler section.  It uses a coupler release button and it also has a shear joint grease zerk, and a universal joint grease zerk.

The shear bolt shears where the universal joint and coupler section meet, allowing the coupler section to turn freely yet stay connected to the universal joint.  This design is easier to service. In my opinion.

The shear point zerk and the universal joint zerk should be greased before you use the PTO shaft and after every eight hours of operation..

The safety shrouds for each PTO shaft are also different designs, so the removal process is different. The wood chipper PTO shaft shroud has three tabs that have to be pressed in to released. It can be difficult to get all three snaps to release with the others reengaging.

When I finally get the shroud loose, I see that the universal joint is pretty clean, so I just remove some of the excess grease.  I repeat the process for the other end of the shaft.

The white plastic ring is one of two sleeve bearings that allow the PTO shaft to rotate independently from the safety shroud.  There is a split in the bearing to allow you to remove it, inspect it and replace it if necessary.  This one looks fine, so I put it back on.

The shroud on the brush hog PTO shaft is held in place by 3 plastic fasteners that are removed by turning counterclockwise a quarter turn then prying them out with a screwdriver.

The sleeve bearing on this shaft is also split for removal but it seems so stiff, I’m afraid it might break if I pull it off, so I inspect it in place and it looks to be in good condition. However, the universal joint is dirty so I clean it up a bit with a paper towel.  Again, I repeat the process for the other end of the shaft.

Next, I separate the sections of the shafts, starting with the short PTO shaft.  Now is a good time to inspect the two sections of the safety shroud.  Other than one end being slight misshapen, they are fine.  No visible cracks, chipping or abrasion.

I inspect the outer section of the shaft for any damage, warping or excessive wear.  It looks good and straight.

Likewise, with the inner section all is well.  Other than some grease, it looks clean, so I don’t wipe it off.  Now for some fresh grease.  I squirt a line of grease along the shaft.  Then rub it all around the shaft.  I squirt another line of grease on the next side, and again I spread it around as evenly as possible.  Finally, I repeat for the third side. This should be done every 20 hours of operation.

Next, it’s time to snap the larger diameter shroud section on to the larger diameter PTO shaft section.  These snap back on a lot easier than they come off!  I repeat for the other section, then slide to two sections of PTO shaft together.  The cross section of the PTO shaft is such that the section will only go together one way.

I grease the sleeve bearings using a pencil-point adapter, and then spin the shroud section on the shaft to spread the grease around. The recommended interval for greasing the sleeve bearings is after every 8 hours of operation.

The process is the same for the brush hog shaft except I wipe the dirt and old grease from it.  Like before, I apply fresh grease to the inner shaft section and spread it around.    Since this shaft gets so dirty, I push a rag through the shroud sections with a broom stick after inspecting them.

Then I re-attach the shroud section by lining up the holes, installing the plastic fasteners: and giving them a quarter turn clockwise. Greasing the sleeve bearing on this shroud is easier because it has an actual grease zerk.  I perform the same steps with the other section and then reassemble the shaft. The last steps for this PTO shaft are to clean and grease the coupler ends.  And finally, I use some oil to lubricate the release collar.

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