JLG 800S Service Manual - Manual (Page 81)

SECTION 3 - CHASSIS & TURNTABLE
3121139 – JLG Lift – 3-35
3.7 TORQUE HUB (4WD MACHINES W/
INTEGRAL BRAKE)
Roll, Leak and Brake Testing
Torque-Hub units should always be roll and leak tested
before disassembly and after assembly to make sure that
the unit's gears, bearings and seals are working properly.
The following information briefly outlines what to look for
when performing these tests.
NOTE: The brake must be released before performing the
roll test. This can be accomplished by either pres-
surizing the brake using the Brake Leak Test proce-
dure below or by tightening the bolts into the piston
through the end plate (See Brake Disassembly Pro-
cedure)
NOTE: Bolts must be removed while performing brake
release test
THE ROLL TEST
The purpose of the roll test is to determine if the unit's
gears are rotating freely and properly. You should be able
to rotate the gears in your unit by applying constant force
to the roll checker. If you feel more drag in the gears only
at certain points, then the gears are not rolling freely and
should be examined for improper installation or defects.
Some gear packages roll with more difficulty than others.
Do not be concerned if the gears in your unit seem to roll
hard as long as they roll with consistency.
THE LEAK TEST (MAIN UNIT)
The purpose of a leak test is to make sure the unit is air
tight. You can tell if your unit has a leak if the pressure
gauge reading on your leak checking fitting starts to fall
after the unit has been pressurized and allowed to equal-
ize. Leaks will most likely occur at the pipe plugs, the main
seal or wherever 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
the o-rings or gaskets meet on 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, and the unit
rechecked. Leak test at 10 psi for 20 minutes.
THE BRAKE TEST
Input Brake - 1,850 in-lb (208 Nm) Static,
225 psi (15.5 bar) Full Release
3000 psi (207 bar) maximum o-ring check.
If brake does not release at these pressure values, brake
has to be inspected, repaired or replaced.
NOTE: Failure to perform this test may result in damaged or
ineffective brake parts.
Tightening and Torquing Bolts
If an air impact wrench is used to tighten bolts, extreme
care should be taken to ensure that the bolts are not tight-
ened beyond their specified torque.
The following steps describe how to tighten and torque
bolts or socket head cap screws in a bolt circle.
1. Tighten (but do not torque) bolt “A" until snug.
2. Go to the opposite side of the bolt circle and tighten
bolt "B" until equally snug.
3. Crisscross around the bolt circle and tighten remain-
ing bolts.
4. Now use a torque wrench to apply the specified
torque to bolt "A".
5. Using the same sequence, crisscross around the
bolt circle and apply an equal torque to the remain-
ing bolts.