JLG 80SL, Service Maintenance Manual

Page: 99 / 162

SECTION 4 - HYDRAULICS
3121325 – JLG Lift – 4-19
Drive Valve
• With no power activating the Valve Coils (1 thru 4), the
machine is in 4 wheel drive low speed. A2 and A1
receive flow from both drive sections of the Main Valve
Block.
• With 24V on Coils 1 and 2, all oil from the pump will
give maximum oil flow through A1 section of the valve
to the front wheels resulting in High Speed 2 Wheel
Drive.
• With 24V on Coils 3 and 4, oil is forced through the flow
dividers as it enters the A1 and A2 ports of the mani-
fold, splitting 50% of the oil to each axle resulting in Dif-
ferential Lock Tractor Drive.
C4 D4 C3 D3 C2 D2 C1 D1
C4
D4
C3
D3
C2
D2
C1
D1
B
P T
A B
PT
AB
B B A
P
T
A B
P T
A B
B B
P T
A B
PT
AB
B A
A A
A A
Passive
Parallel 4-Wheel Drive
Active
Fast 2-Wheel Drive
Active
Posi-trac 4-Wheel Drive
Rear Front Rear Front Rear Front
Drive 2
Valve Drive 1
Valve
Drive 2
Valve
Not Used
Drive 1 Valve
Active
Drive 2
Valve Drive 1
Valve
SCHEMATIC
C4 D4 C3 D3 C2 D2 C1 D1
C4
D4
C3
D3
C2
D2
C1
D1
C4 D4 C3 D3 C2 D2 C1 D1
C4
D4
C3
D3
C2
D2
C1
D1
Figure 4-36. Drive Valve