JLG 4394RT Service Manual - Manual (Page 44)

SECTION 3 - CHASSIS & SCISSOR ARMS
3-8 – JLG Sizzor – 3121133
3.4 INTEGRATED TORQUE/DRIVE HUB
The Integrated Torque/Drive Hub is an axial piston-hydrau-
lic motor with integrated, hydraulic released multi plate
parking brake and a 2-stage planetary gearbox and a dis-
connect mechanism.
To insure an optimum balancing of loads, each planetary
stage comprises of planet gears in sets. The externally
toothed wheels are case-hardened.
The hydraulically released, wet running, multi plate brake,
integrated in the hydraulic motor, is a parking brake. It is
normally closed by spring force and released when pres-
surized by hydraulic oil.
NOTICE
TORQUE HUB UNITS SHOULD ALWAYS BE ROLL AND LEAK
TESTED BEFORE DISASSEMBLY AND AFTER ASSEMBLY TO
MAKE SURE THAT THE UNIT’S GEARS AND SEALANTS ARE
WORKING PROPERLY.
Roll Test
The purpose of a roll test is to determine if the unit’s gears
are rotating freely and properly. Gears should be able to
be rotated by applying a constant force to the roll checker.
If more drag is felt in the gears only at certain points, then
the gears are not rolling freely and should be examined for
proper installation or defects. Some gear packages roll
with more difficulty than others. Do not be concerned if
gears seem to roll hard as long as they roll with consis-
tency.
Leak Test
The purpose of the leak test is to make sure the unit is air
tight. The unit has a leak if the pressure gauge reading on
the air checker starts to fall once the unit has been pres-
surized. Leaks will most likely occur at main seal or wher-
ever o-rings or gaskets are located. The exact location of
a leak can usually be detected by brushing a soap and
water solution around the main seal and where o-rings or
gaskets meet the exterior of the unit, then checking for air
bubbles. If a leak is detected in a seal, o-ring, or gasket,
the part must be replaced.
.
Table 3-3. Torque/Drive Hub Specs
Gearbox
Maximum Output Speed 30.25 rpm
Maximum Output Torque 4556.5 lb ft (6177.7 Nm)
Brake
Static Brake Torque 88 lb ft (119.3 Nm)
Release Pressure 174 psi (12 bars)
Motor
Maximum Displacement 28 CCM
Minimum Displacement 14.2 CCM
Switching Pressure 145 psi min - (1450 psi) max
X3
MB
A B
X
T
MA
Figure 3-7. Integrated Torque/Drive Hub
NOTE: JLG P/N’s: 2780263 (2WD), 2780262 (4WD)