JLG 1850SJ Service Manual - Manual (Page 251)

SECTION 5 - BASIC HYDRAULIC INFORMATION & HYDRAULIC SCHEMATICS
3121619 – JLG Lift – 5-81
5. Transmission Drives in one direction only
a. Are electrical connections to pump control propor-
tional solenoids correct, intact and without defects?
Yes - Proceed to step 5.b
No - Rectify the problem
b. Check hot oil flushing valve cartridge #120 located
in the Traction Control Manifold.
Remove and inspect flushing valve cartridge for
stuck spool or damaged cartridge O-ring seals &
backup rings.
c. Inspect "Make-Up" check valve cartridges, #190.1-
190.4, installed in the Traction Control Manifold. Is a
cartridge "stuck" open with debris or is an O-ring
failed?
No - Proceed to step 5.d
Yes - Clean/repair or replace Make-Up check car-
tridge.
d. Swap high pressure relief valves in the transmission.
Does the transmission drive in the other direction?
No - Proceed to step 5.e
Yes - Repair/clean/adjust or replace high pressure
relief valve on the non-driving side
e. Replace "EP" control module. Does pump operate
properly?
No - Replace or repair pump
Yes - Operate the transmission
6. Transmission Drives in Wrong Direction
a. Check to see if electrical connectors or wiring have
been swapped on the pump.
b. Check to determine want end of the machine the
boom is swung over.
7. Transmission Does Not Find or Hold Neutral
a. Does pump remain in neutral with electrical con-
nectors removed?
No - proceed to step 7.b
Yes - Check electrical system for signal problem
b. With electrical connectors removed and machines
wheels jacked off the ground and engine running,
momentarily apply 12 volt DC signal (battery volt-
age) to a pump control solenoid. Does the pump
return to neutral after the 12 volt signal is removed?
No - Apply 12 volts to opposite solenoid & recheck.
No - Replace pump control module, repeat step 7.a
Yes - Possibly dirt was dislodged from control mod-
ule, re-check thoroughly to determine problem has
definitely been resolved.
c. Check mechanical centering of the pumps
8. Transmission Drives at a High Noise Level
a. Are the wheel drive planetary reduction gearboxes
filled to the correct level and do they have the
proper lubricant?
No - Fill gearbox with correct grade of oil to the pre-
scribed level.
Yes - Proceed to step 8.b
b. Is the engine flex plate and drive coupling correctly
installed and aligned with the transmission pump?
No - Install flex plate and bell housing per manufac-
turer's instructions
Yes - proceed to step 8.c
c. Is a rigid item or object contacting the resilient
mounted engine/pump assembly?
No - Proceed to step 8.d
Yes - Ensure no item is contacting the unit, transmit-
ting air borne noise.
d. Is the suction pressure/vacuum at the charge
pumps inlets within recommended limits?
No - Return to step 1.h
Yes - Proceed to step 8.e
e. Is there air in the hydraulic fluid? This may be indi-
cated by foaming or milky colored oil.
No - Proceed to step 8.f
Yes - De-aerate the oil and inspect system for cause
of air induction. Check for loose or missing O-rings
on face seal connections.