Top Link
The single length-adjustable link that forms the apex of the three-point hitch. Changing its length adjusts the forward or backward tilt of the implement; on ploughs and cultivators this tilt directly determines working depth and the implement's entry angle into the soil. It is usually adjusted with a right-and-left threaded turnbuckle.
The top link does not carry most of the load, it sets the geometry. When shortened, the front of the implement tips down; when lengthened, the rear digs in. The most common reason for getting a different depth with the same hydraulic command is that the top link setting has changed.
- On ploughs and subsoilers the top link works under compression, on cultivators it is mostly under tension.
- Systems that read this compression force through a spring or a sensor perform top-link draft sensing.
- When making the length adjustment, do not forget to tighten the lock nut; a loose turnbuckle can turn by itself during work.
The electronic retrofit kit does not interfere with the top link. Since LFT20 and LFT54 pull the tractor's quick lift cable, the hitch raise/lower command becomes electronic; the angle of the implement still depends on the top link setting. So even after fitting the kit you must first set the correct depth mechanically from the top link, then take the repeatable command from the electronics.
Context in which this term is used: Converting a tractor hydraulic lever to electronic control