Key Takeaways

• Three-point hitches use a five-category standardization system, Categories 0 through 4, keyed to tractor horsepower so components from any manufacturer will fit correctly within the same category.

• The three core components are a top link and two lift arms (also called lower links), which allow the operator to raise, lower, or tilt the implement independently of tractor movement.

• Top link and lift arm pin diameters are fixed by category. Ordering the wrong category means pins and ball holes will not match.

• Conversion lift arm pins and conversion bushings let you bridge size differences when the tractor and implement are different hitch categories.

• Power Take-Off (PTO) adapters are required when the tractor and implement are in different hitch categories and the splined shafts do not match directly.

Grab a top link off the shelf without knowing your hitch category, and there is a reasonable chance the pin will not fit. With dozens of tractor and implement manufacturers producing equipment across a wide horsepower range, the three-point hitch (3PH) uses a five-category standardization system to keep everything interchangeable. Categories are numbered 0 through 4 and keyed to tractor horsepower. Each category specifies fixed pin diameters for both the top link and lift arms, so components from any manufacturer will fit correctly when the categories match. RBH stocks three-point hitch components across all five categories.

What Is a Three-Point Hitch?

A three-point hitch is the mounting system used to attach implements such as plows, mowers, and cultivators to the rear of a farm tractor. The name comes from its three core components: a top link and two lift arms, sometimes called lower links. By raising or lowering the lift arms and adjusting the top link length, the operator controls implement position, including mower height and plow depth, rather than simply dragging the implement behind the tractor. 

The top link is adjustable in length, functioning similarly to a large turnbuckle. It has a ball pivot at each end for attachment to both the tractor and the implement. The lift arms also use ball pivots at each end but are fixed in length.

Why Are There 5 Hitch Categories?

With a large number of tractor, implement, and hitch component manufacturers producing equipment at different scales, a standardized category system simplifies compatibility. Rather than matching by brand, operators select components by category number, which is based on tractor horsepower. Components within the same category, regardless of manufacturer, use identical pin diameters. This means a top link from one manufacturer will accept a pin from another as long as both are the same category. 

The five categories and their specifications are: 

What Are the Main Components of a Three-Point Hitch?

The three-point hitch system includes the top link, lift arms, and the pins, fasteners, and adapters that connect them to the tractor and implement. Top links are available in several lengths depending on the application, but the ball hole diameter at each end is standardized by category. They attach to both the tractor and implement via top link pins, which vary in length but have standardized diameters by category. 

Lift arms attach to the tractor with a bolt or stud and connect to the implement via lift arm pins. Lift arm pins are available in fixed and adjustable versions. Adjustable versions have no shoulder and use two nuts for mounting, offering more flexibility in positioning. Both types use a lynch pin to hold the arm in place.

What Are Top Link Pins and Lynch Pins?

Top link pins secure the top link to both the tractor and implement. Pin lengths vary, but diameters are standardized by hitch category. Each pin is retained with a lynch pin passed through the hole at the end of the top link. Lynch pins are most commonly available in 1/4", 5/16", and 7/16" diameters.

What Are Lift Arm Pins, Conversion Pins, and Conversion Bushings?

Standard lift arm pins attach lift arms to the implement and are available in fixed and adjustable versions. When the tractor and implement are from different hitch categories, two adapter components bridge the size difference: 

What Are Replacement Ends and Adjustable Side Links?

Replacement ends can be used to rebuild worn top links and lift arms rather than replacing the entire component. They are ordered by category number, the same as the original parts.

Adjustable side links are necessary for hitch operation because they raise or lower the lift arms to the desired position. The upper ends of the side links attach to the frame of the tractor.

When Do You Need a PTO Adapter?

The Power Take-Off (PTO) is a splined shaft that protrudes from the rear axle of the tractor. It drives the moving parts of implements such as rotary mowers by sliding into a splined coupling on the implement. When the tractor and implement are different hitch categories, a PTO adapter mates the different shaft and coupling sizes and is held in place with a PTO lock pin. 

If both the tractor and implement are the same hitch category, the splined PTO shaft slides directly into the implement coupling with no adapter required.

What Are Hitch Pins and When Are They Used?

Hitch pins are used with towed implements rather than mounted ones. A towed implement has a forked tongue with holes that slip over the tractor's drawbar, and a hitch pin passes through both to hold them together. Hitch pins come in a wide variety of sizes and are available in several head styles, including spring-clip, D-ring, and chain-retained versions. All are held in place with a lynch pin.

Need Help?

If you are sourcing three-point hitch components, including top links, lift arm pins, conversion hardware, or PTO adapters, RBH stocks parts across all hitch categories and can help you identify the right fit for your tractor and implement combination.

Contact us today or call us at 800-669-9650 to speak with a member of our customer service team. We have 11 locations across the Southeast and Midwest, including Knoxville, TN; Marietta, GA; Orlando, FL; Charlotte, NC; Little Rock, AR; Fort Worth, TX; Benton, IL; Madisonville, KY; Princeton, WV; Birmingham, AL; and Calvert City, KY.