JLG M600 Service Manual - Manual (Page 139)

SECTION 4 - BOOM & PLATFORM
3121813 – JLG Lift – 4-29
Inspection
Inspect all parts for wear, damage, cracks, etc.
HOUSING
Inspect the cylinder bore for wear and scratches. The sur-
face finish should be 32 RMS or better. Rehone if neces-
sary. Minor scratches and damage can be repaired by
local polishing. Inspect all bearing contact surfaces for
damage and/or contamination and repair and clean as
necessary. Inspect the exterior of the housing for damage,
cracks, integrity of welds, etc.
SHAFT
Check the sealing surface of the shaft for scratches and
damage. Polish if necessary.
GEAR COMPONENTS
Check gearing for excessive wear. Nominal movement
between gear components in excess of 1.5 degrees can
result in sloppy response.
BEARINGS
All radial bearings are of a reinforced nylon material. If the
thickness measures less than 0.123 in. (3.125 mm), the
bearings should be replaced.
THRUST WASHERS
Manufactured from an orkot material. If the thickness mea-
sures less than 0.113 in. (2.870 mm), or if contaminants
are noticed imbedded in the material, the thrust washers
should be replaced.
Reassembly
It is recommended that you first practice assembling the
actuator with the bearings and thrust
washers i nstalled
but without the seals. The seals are easily damaged and
their increased friction makes assembly more difficult. Be
sure that the timing
marks o n the gear components are
engaged in the correct orientation. Mark the timing marks
with a felt tip marke r for better visibility to make assembly
easier.
1. Wash all parts thoroughly in cleaning solvent and
blow dry.
2. Pump a high quality NLGI-2 lithium based grease
into the grease fittings (111) to flush any contami-
nants out of the fittings and passages and to insure
the fittings are functioning properly. Replace any
non functioning fittings. Wipe off all excess grease.
The set screws of the relief valves (112) must be
flush with the countersunk bore to ensure proper
tension on the spring as seen in Photo F. If the set
screws are threaded in too far, the seals will be
extruded during greasing and damaged. Secure the
set screws with Loctite#
242.
3. Lightly coat the thrust washers (304) with grease
and install them on the shaft (02) and end cap (04)
prior to seal installation.
4. Lightly coat all sealing and working surfaces with a
good grade of hydraulic oil.
5. Install all seals in their respective grooves. Refer to
the Assembly Drawing on page 2 to ensure the cor-
rect orientation of all seals. Note that the 0-ring ener-
gizer should be removed from seal (201) on the
inside diameter of the piston nearest the piston
splines. This prevents pressure from being trapped
between seals (200) and (201).
6. With the housing positioned horizontally and firmly
secured to prevent movement, insert the piston
sleeve into the housing bore until the piston seal
contacts the housing chamfer. Look through the
opposite side (shaft flange side) of the housing bore
and rotate the piston sleeve as necessary to align
the timing marks on the housing ring gear and pis-
ton sleeve. While holding the piston sleeve steady to
prevent damage to the cylinder bore, drive the pis-
ton sleeve into the housing with a rubber mallet until
the gear teeth engage. This assembly step is difficult
and might require several attempts to successfully
engage the gear teeth. Double check the timing
marks and the engagement of the gear teeth to
insure correct alignment, then drive the piston
sleeve as far as possible into the housing until it
comes to a stop against the ring gear.
7. Install the shaft as seen below in timed relation to
the piston sleeve by aligning the punched timing
marks as shown below. Temporarily taping the
threaded portion of the shaft with masking tape will
make it easier to clear the rod seals and prevent
their damage Once the gear teeth are engaged,
rotate the shaft clockwise until it is bottomed out
against the piston sleeve. Using a rubber mallet,
drive the shaft into the housing until the thrust