JLG TF6-42 Service Manual - Manuale (Pagina 672)

T12000 ID 04/99 6-3
6.1.2 The input shaft and directional clutches
The turbine shaft driven from the turbine transmits power to the forward, 4th-High or reverse clutch.
These clutches consist of a drum with internal splines and a bore to receive a hydraulic actuated piston.
The piston is oil tight by the use of sealing rings. The steel discs with external splines, and friction discs
with internal splines, are alternated until the required total is achieved.
A back-up plate is then inserted and secured with a retainer ring. A hub with outer diameter splines is
inserted into the splines of discs with teeth on the inner diameter. The discs and hub are free to increase in
speed or rotate in the opposite direction as long as no pressure is present in that specific clutch.
To engage the clutch, the solenoid will direct oil under pressure through tubes and passages to the selected
clutch shafts.
Oil sealing rings are located on the clutch shafts. These rings direct the oil through a drilled passage in the
shaft to the desired clutch.
Pressure of the oil forces the piston and discs against the back-up plate. The discs with splines on the outer
diameter clamping against discs with teeth on the inner diameter enables the drum and hub to be locked
together and allows them to drive as one unit.
When the clutch is released, a return spring will push the piston back and oil will drain back via the solenoid,
the bleed valve or holes in the clutch piston into the transmission sump.
These bleed valves will only allow quick escape of oil when the pressure to the piston is released.
The T12000 transmission, 3-speed version, has one reverse clutch and one forward clutch. This in combination
with the 3 range clutches results in the transmission having 3 forward and 3 reverse speeds.
The T12000 transmission, 4- and 6-speed versions, have one reverse clutch and two forward clutches (forward
and 4th-High). This in combination with the 3 range clutches results in the transmission having 4 forward (for
the 4-speed) or 6 forward (for the 6-speed) and 3 reverse speeds.
The engagement of the directional clutches (forward and reverse) are modulated. This means that clutch
pressure is built up gradually. This will enable the unit to make forward, reverse shifts while the vehicle is still
moving and will allow smooth engagement of drive. The modulation is done hydraulically.
1 ST 2 ND
4 TH -H I 3 RD
3 RD
REV FWD
THE INPUT SHAFT AND DIRECTIONAL CLUTCHES
Operation of the transmission