Third-Function Kits: How to Add a Hydraulic Valve to a Tractor
Adding functionality to your bucket loader with a third function kit.
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Third-function valve kits are a great way to add utility to your tractor; learn how to add a hydraulic valve to a tractor to increase your machinery’s functionality.
by Jeremy Chartier
Third function kits are a great way to add utility and ability to your tractor. Just like how adding a thumb to a backhoe adds a whole new dimension of functionality, having a grapple on your bucket or the ability to swing a snow plow left to right can massively change what you can accomplish with your tractor.
Third Function Kits
I opted to purchase a kit from W. R. Long for my application. I had to purchase it through my local tractor dealership, but I called W. R. Long directly to get the correct part number for the kit. Since there were multiple build options for my 2002 John Deere 5105, they took a minute to walk me through the options. I paid full price for this kit as a regular customer. Nothing was supplied to me as a reviewer or author, and I received no special treatment. Customer service was thorough, and they were happy to help me.
Custom Or Universal
Thankfully, companies like W. R. Long and Summit Hydraulics offer complete kits to convert a tractor without a front auxiliary function, removing the guesswork from the installation. John Deere and Kubota offer OEM solutions for adding a third function, and these kits are usually a more refined solution at a more refined price. Universal kits are available for those who welcome a challenge, or you can piece one together with little effort.
Constant Flow Vs. Momentary
Third function kits come in two general functions: momentary and constant flow. Constant flow valves operate hydraulic motors on attachments such as a front-mounted bush hog or hydraulic post-hole auger. In this setup, you would activate your function kit, and a continuous flow of hydraulic fluid would spin the hydraulic motor attached to the outputs. Deactivating the circuit would stop the motor from rotating.
The more popular choice is the momentary style function, which will operate pistons. An example of this would be a grapple bucket or front-mounted log splitter. In this configuration, one switch would open your grapple while you held the button down, releasing it to stop. The other button would clamp the grapple down.
Power Beyond Vs. Diverter
Third function kits need hydraulic power to operate, and they can acquire it in two main ways. The kit I purchased interrupts the power beyond, or hydraulic feed line, that would otherwise feed my bucket valve controls. Placing this new valve between the hydraulic feed and the controls of my bucket means that I will have reduced force in my loader’s up, down, and tilt functions while the third function is actively in use. The original force returns as soon as I release the function buttons. Because the electronic valve controls the function with an on or off condition, you don’t get that fine control your tractor’s loader valve stick would offer when using the third function.
Diverter kits are installed downstream of the tractor’s hydraulic controls. In this configuration, the bucket tilt or loader lift function is switched with the activation of the function kit. If you switched your bucket tilt function, the normal controls for your bucket would swap to controlling the third function until you deactivate the third function circuit. Once deactivated, your hydraulic controls for the bucket will return to normal.
Accessing The Valve Body
Every tractor is different, and installing these kits may be easier or harder, depending on your model. From the online sleuthing I’ve done, it looks like many John Deere compact tractors require you to remove the right tire and fender to access the power beyond port. This isn’t an impossible project, but it adds time and effort. My John Deere has the loader control valves tucked under the right side operator’s platform, forward of the fender. This means I, thankfully, don’t need to pull my fender to access the power beyond line.
Identifying Power Beyond
There’s no universal indicator of which line is the power beyond. Some manufacturers include a green indicator on the line, and some use some sort of extended fitting, but the only way I could deduce which line was which was by process of elimination. Like many valve bodies, I have seven lines. The four that fed my loader were easy to trace, but the last three offered a challenge. I have a lever-actuated valve that operates the hydraulic function in the back of my tractor, and at first look, all three lines led back to that valve. After searching and stuffing my phone behind the fender to take pictures, I could trace which line I needed to interrupt to make my third function kit work.
Mounting Hardware
The electronic valve I have has a mounting plate, and there are two large bolts on the right side of the tractor that the bracket works with. It’s a simple affair of unbolting these bolts, placing the bracket correctly, and bolting it back together. The front fittings for the loader are a different story. Given how my loader was built, I will be welding the bulkhead for those fittings to the crossbar of my loader. W. R. Long suggests this or bolting it on. I’m not about to drill holes for that, so welding it is.
Routing Hoses
One disadvantage of an aftermarket kit is that hoses go from the valve to the front loader, unlike OEM kits that may supply pre-bent hard lines. There’s no tidy way of running these hoses, so grab some industrial-grade zip ties and secure them to your OEM hard lines or line brackets. Make sure to carefully pivot your loader up and down before committing to your hose placement to verify there’s enough slack to allow the hoses to move with the loader safely, avoiding stretching or pinching of the hoses.
At 12 years old, Jeremy Chartier became involved with his local 4-H group, later joined the local FFA chapter, and showed livestock until his college years. After graduating from the Ratcliffe Hicks School of Agriculture at UConn, he joined the University of Maine’s Poultry Service Provider training program. Today Jeremy sells started pullets to local backyard farmers, is still involved with 4-H as a poultry showmanship judge, and writes about his passion for farming.
Originally published in the March/April 2025 issue of Countryside and Small Stock Journal and regularly vetted for accuracy.
