JLG 600SC_660SJC Service Manual - Manual (Page 100)

SECTION 5 - CAT CHASSIS (S/N 0300128000 TO PRESENT)
5-8 – JLG Lift – 3121157
Two-Speed Changeover System
Structure of two-speed changeover system
Swash plate has three faces, "A" through "C" as shown in
Figure 5-8., and is held against the flange holder by two
steel balls in a tiltable state. The two-speed changeover
valve is installed inside the base plate.
Operation of Two-Speed System
Refer to Figure 5-9.
If pilot pressure for changeover is exerted on the 2-speed
changeover valve from port Ps, the 2-speed changeover
valve is changed as in the figure, with motor driving pres-
sure exerting on the 2-speed control piston. This pushes
up the swash plate, which tilts and rolls to a position
where the resultant of thrust of piston sub assembly and
spring force is balanced with thrust of the 2-speed control
piston. The swash plate is settled when its side B contacts
the flange holder. The swash plate inclination becomes ß,
obtaining speed two (high speed) rotation for the motor.
Figure 5-8. Structure of Two Speed Changeover System
Figure 5-9. Structure of Two Speed Changeover System at High Speed