JLG 660SJ Service Manual - Manual (Page 138)

SECTION 5 - HYDRAULICS
5-6 – JLG Lift – 3120840
5. Carefully slide the piston spacer on the rod.
NOTE: Upper telescope cylinder piston has an o-ring
installed inside the spacer.
6. If applicable, correctly place new o-ring in the inner
piston diameter groove. (The backup ring side fac-
ing the O-ring is grooved.)
7. If applicable, correctly place new seals and guide
lock rings in the outer piston diameter groove. (A
tube, with I.D. slightly larger than the O.D.of the pis-
ton is recommended to install the solid seal.)
NOTE: The backup rings for the solid seal have a radius on
one side. This side faces the solid seal.(See magni-
fied insert in Figure 5-10.)The split of seals and
backup rings are to be positioned so as not to be in
alignment with each other.
8. Using suitable protection, clamp the cylinder rod in
a vise or similar holding fixture as close to piston as
possible.
9. Carefully thread the piston on the cylinder rod hand
tight, ensuring that the o-ring and back-up rings are
not damaged or dislodged.
10. Thread piston onto rod until it abuts the spacer end
and install the tapered bushing.
NOTE: When installing the tapered bushing, piston and mat-
ing end of rod must be free of oil.
WHEN REBUILDING THE MASTER, SLAVE, LOWER LIFT, UPPER
LIFT, ARTICULATING FLY BOOM LIFT, UPRIGHT LEVEL, TOWER
TELESCOPE, OR UPPER TELESCOPE CYLINDERS, TIGHTEN
SECURELY. (SEE TABLE 2-1 AND 2-3. TORQUE SPECIFICA-
TIONS).
11. Assemble the tapered bushing loosely into the pis-
ton and insert JLG capscrews (not vendor cap-
screws) through the drilled holes in the bushing and
into the tapped holes in the piston.
12. Tighten the capscrews evenly and progressively in
rotation to the specified torque value. (See Table 5-1,
Cylinder Head and Tapered Bushing Torque Specifi-
cations. (S Models) and Table 5-3, Cylinder Head
and Tapered Bushing Torque Specifications. (A
Models).
Figure 5-10. Piston Seal Kit Installation
Figure 5-11. Tapered Bushing Installation