PTO (power take-off) shafts mechanically transfer power from a tractor engine to an attached implement, the implement then uses that power to operate its machinery. The most common types of tractor PTO shafts are often referred to as “Italian” or “German” style.
There are three principal types of PTO. Transmission, live (two stage clutch) and independent. The simplest type is transmission, with the PTO directly linked to the tractor's transmission system. The downside being when the tractor is out of gear the PTO will stop working. A live PTO allows the operator to change gear or slow down without losing power, whilst an independent PTO means the shaft is controlled by a separate clutch.
Component Parts of a PTO Shaft
PTO shafts consist of two ends with an outer yoke, cross and an inner yoke. Running between the two ends is the PTO tube and tube guard, retainer clips and safety chains.
Identifying the Correct PTO Shaft
The first task when replacing a PTO shaft is to establish exactly what series and type the shaft is. To do this, first look at the tube profile. This will either be lemon, star or triangular in shape or it may be splined. Secondly, measure the universal joint/cross to establish its size.
Use the tube profile and universal joint/cross size in conjunction with distributors' or manufacturers' printed guides and the correct series and type of PTO shaft will be revealed. An added factor will be the length of shaft required which will also be brought into the equation.
When working in close proximity to a PTO shaft it is worth bearing in mind health and safety. It is essential to make sure that any PTO shaft has a fully functioning safety guard. It is also worth remembering that a defective safety guard can be as lethal as no guard at all.