A JCB backhoe loader has uniqueness to itself. It does not have a normal gear box just like your car or other heavy vehicle. It has a automatic transmission. To a automatic transmission two parts are every critical to it, one is a torque convertor and another is a transmission pump ( more commonly called as a charging pump).
A charging pump can be referred to as a heart of automatic transmission. It creates required pressure of transmission fluid to help the transmission function. An transmission pump is basically a gear pump. It contains two set of gears. The inner gear is rotated by the torque convertor. The second gear is mated with the inner gear, upon rotation of inner gear it rotates the outer gear. By rotation of gears the suck the oil from one chamber and pump them out through the other chamber.
The high pressure oil by transmission pump is used to function valves in the valve body and to apply clutch plates and bands. Common problems with the transmission pumps include:
a.) Assembly mistakes by the manufacturer or illiterate mechanic
b.) Worn out gasket so wrong size gasket
c.) Worn out gears
d.) Worn out tolerances between the inner gear and outer gear
e.) Worn out tolerances at the front and back of the pump.
A Charging Pump is essentially a gear pump, just like the Hydraulic Pump. Just as hydraulic pump pumps hydraulic oil throughout the machine, a Charging Pump pumps transmission oil from torque convertor to the transmission unit. Since a Charging Pump has to pump fairly less amount of oil to a fairly less distance at fairly less pressure, therefore it is very small in size. Proper fitment of charging pump is very much important for its functioning, a lot many times mechanics while fitting the pump disassembles and while reassembling it they put gears on the wrong side as a result the pump does not function well and does not provide the required pressure.
This results in the customer suffering. One should always visit only trained mechanics for the fitment of charging pump. Once should always take care that the teeth of Charging Pump and Torque Convertor mates properly , because if the teeth do not mate properly both Charging Pump and Torque Convertor can get damaged, resulting in huge looses for the customer.
While replacing a charging pump one can go either for a JCB genuine pump or for a aftermarket pump. While buying a aftermarket pump one should go for Robot brand pump. Robot is the only JCB parts manufacturer which manufacturers transmission pump on high precision CNC machines and all the transmission pumps are checked for quality. While buying for JCB spare parts one should take utmost care to use only high quality JCB parts.