JLG 41AM (3120752) Service Manual - Manual (Page 48)

SECTION 2 - SERVICE PROCEDURES
2-24 – JLG Lift – 3120752
2.9 MAST ASSEMBLY
(See Figure 2-3., Figure 2-4. or Figure 2-5.)
Mast Section 1 - Assembly
(All Masts)
1. Place mast section-1, rail (open) side up (See Figure
2-2.) on a clean, flat surface (preferably a table or
work bench capable of supporting the weight of the
entire mast assembly). Slide mast out over end of
work surface far enough to allow access to the chain
anchor attach holes at top of mast.
2. Locate the two (2) single (wide) chain assemblies.
Lay out each chain assembly with anchor block end
towards mast, and notched end of block down, (be
certain floor surface is clean and free of any metal
chips or debris which may stick to lubricated chains
or lay chains in a clean bucket).
3. Insert the block anchor end (with notched end on
bottom) into the top of mast section-1 and secure
using two (2) 3/8"-16UNC x 2-1/2" long hex head
bolts, flatwashers and nuts for each attach block.
Place a flatwasher under bolt head and nut.
Mast Section 2 - Assembly
(All Masts)
NOTE: When sliding mast sections together, be careful not
to scratch or score the anodized finish in the slide
pad channels.
4. Locate mast section-2, carefully slide mast section-2
closed rail into section-1 open rail. Slide sections
together until ends are even.
5. Insert slide pads into the slide pad channels at bot-
tom end of mast between section-1 and -2, (one on
each side of the mast), with beveled surface facing
out towards section-1.
6. Thread slide pad attaching bolts, (two (2) 1/4"-
20UNC x 3/8" long hex head bolts, place a flat
washer under head of each bolt), through holes in
mast section-2 inside rail, into the slide pad inserts.
Thread in enough to hold pad in place.
7. Shim slide pads using the following steps:
NOTE: Always use an even amount of shim material behind
slide pads on both sides of the mast rails. This will
keep mast sections centered in rail channels and
prevent any distortion of the mast section.
a. Start with a .036" thick shim and a .075" thick
shim per side at each slide pad.
b. Slide shims into place between slide pad and
mast rail. Tighten the slide pad mounting bolts,
be sure there are no air gaps between shims,
shim and mast or shim and slide pad when tight-
ened.
c. Check mast section for side play. If play exists
add .015" shims dividing the thickness equally
between both sides of mast. Insert shims until
the shims cannot be inserted halfway by hand
with the mast pulled to the opposite side.
d. When mast slide pads are shimmed properly,
there should be no side to side movement of
slide pad in rail channel. Mast sections should
be snug in channels but still be able to slide in
channel by hand.
8. Insert slide pads into the slide pad channels (top of
mast) between section-1 and -2, (one on each side
of the mast), with beveled surface facing in towards
section-2.
NOTE: Before fastening and shimming the slide pad on the
top left side of the mast, install a sequence cable
bracket against the mast under the flatwasher.
9. Thread slide pad attaching bolts, two (2) 1/4"-
20UNC x 3/8" long hex head bolts, place a flat
washer under head of each bolt, through holes in
mast section-1 outside rail (top of mast) and into the
slide pad inserts. Thread in enough to hold pad in
place.
10. Shim per instructions in step 7, Mast Section 2 -
Assembly.
NOTE: If hydraulic cylinder needs to be extended, the pro-
tective caps on the extend and return ports will need
to be removed. Be careful not to nick or scour rod
surface when extending, also catch any oil draining
out of cylinder to avoid spillage onto work area.
11. Locate the hydraulic lift cylinder, slide the lift cylinder
into the closed rail side of mast section-2 with rod
end to top and port end to bottom of mast. Cylinder
should extend out of mast on both ends. Mount the
cylinder with the manual descent valve assemby fac-
ing the back of the mast, towards mast section-1.
12. Original Design Cylinder Mount: Install the cylin-
der mount and cylinder mounting plates into the bot-
tom of the mast section-1. Shim to eliminate any
side clearance to prevent any strain on the sides of
the mast when the bolts are tightened.
13. New Design Cylinder Mount: Install the cylinder
mounting plates at the bottom of the mast section-1.
Mount plates two each side, using the the (2) two
long pass through bolts and nuts, apply Loctite
#242 to the bolt threads before tightening nuts.
14. Original Design Cylinder: Clamp the cylinder in the
mounting journal of the cylinder mount. Apply Loc-
tite #242 to the journal bolt threads and torque to 85
ft. lbs. Align the hole in the mounting journal with the
hole in the cylinder and Install the (1) 5/16" bolt.