What is the difference between cat 2 and cat 3?

The difference between Cat 2 and Cat 3 is size and capacity of tractor three-point hitch for medium versus large farm tractors. Category 2 is for utility tractors 40 to 100 horsepower, with lower link pins 1-1/8 inch diameter, top link pin 1 inch diameter, spacing between lower arms about 32 inches, lift capacity 3000 to 5000 pounds, used for 6 to 8 foot implements like heavy rotary cutters, disc harrows, and large box blades for mid-size farms. Category 3 is for large agricultural tractors 80 to 225 horsepower, with bigger pins lower 1-7/16 inch diameter, top 1-1/4 inch, spacing about 38 inches, lift capacity 5000 to 8000 pounds or more, used for heavy tillage implements like large plows, heavy discs, and big balers for large commercial farms. Physically, Cat 3 hitch arms, pins, and hydraulic cylinders are much thicker and stronger to handle greater draft forces. Cost difference, Cat 3 implements are more expensive and heavier. Compatibility, you can use Cat 2 implements on Cat 3 tractor with bushings that adapt smaller pins to larger holes, but not Cat 3 implements on Cat 2 tractor as they are too heavy and would overload hydraulics and cause instability. PTO horsepower also differs, Cat 2 tractors have 35 to 90 PTO horsepower, Cat 3 have 70 to 200 PTO horsepower to run heavy implements.