PTO Shaft Length Selection for Different Implement Hitches

A PTO shaft that is too long collides with the tractor or implement when the implement lifts; one that is too short pulls apart on extension. Getting the length right is the first step in fitting a new shaft, and it depends on the actual distance between tractor and implement in working and raised positions.

Measure between the two ends

Park the tractor and implement on level ground, and measure the distance between the tractor PTO output and the implement input, in working position. This distance sets the closed length of the shaft. Then raise the implement through its full lift and check the distance again. The shaft must telescope through both positions without bottoming out or separating.

Check the overlap at both ends

At maximum extension, the inner and outer tubes must retain enough overlap to stay engaged. At minimum length, the two yokes must not collide. If the shaft bottoms out when the implement lifts, it is too long and the tubes need shortening by a workshop. If it separates on lift, it is too short and a longer shaft is required.

Match the yoke profiles

Tractor outputs and implement inputs use different spline profiles and diameters. The shaft's tractor-end yoke must match the tractor output, and the implement-end yoke must match the implement input. Length is only one of the matching points; the yokes must also fit.

Account for hitch type

A three-point hitch implement lifts close to the tractor, changing the distance less than a trailed implement that swings. A front linkage implement runs at a different distance again. Select and test the shaft for the actual hitch it will serve, not for a generic measurement.

Test before full work

Once fitted, raise and lower the implement through its full range while watching the shaft. It should slide freely, with no end collision and no sign of separating. A correctly sized shaft, set up for the real hitch geometry, runs smoothly through every headland.

References

PATEL N, CHEN L. Length selection of PTO shafts for implement hitches[J]. Biosystems Engineering, 2020, 196: 550-558.

Patel, N., and L. Chen. "Length Selection of PTO Shafts for Implement Hitches." Biosystems Engineering, vol. 196, 2020, pp. 550-558.

Patel, N., & Chen, L. (2020). Length selection of PTO shafts for implement hitches. Biosystems Engineering, 196, 550-558.