April 2018 Service and Repair ManualBoom ComponentsPart No. 1279835GT ZX®-135/70 674-7Secondary Boom ExtensionCylindersThe secondary boom extension cylinders extendand retract the secondary boom. The secondaryboom extension system consists of 3 hydrauliccylinders and each are equipped withcounterbalance valves to prevent movement in theevent of a hydraulic line failure.How to Remove the SecondaryBoom Extension CylindersBodily injury hazard. Thisprocedure requires specific repairskills, lifting equipment and asuitable workshop. Attemptingthis procedure without these skillsand tools could result in death orserious injury and significantcomponent damage. Dealerservice is strongly recommended.Note: When removing a hose assembly or fitting,the O-ring (if equipped) on the fitting and/or hoseend must be replaced. All connections must betorqued to specification during installation. Refer toSpecifications, Hydraulic Hose and Fitting TorqueSpecifications.Note: Perform this procedure with the machine ona firm, level surface and in the stowed position withthe axles extended.1 Raise the primary boom approximately 10 feet/ 3 m. Turn the machine off.2 Working at the platform end of the secondaryboom, support and secure the secondaryboom end cover to a suitable lifting device.3 Remove the cover retaining fasteners andremove the cover from the secondary boom.Crushing hazard. The secondaryboom end cover could becomeunbalanced and fall whenremoved from the secondaryboom if not properly supportedand secured to the lifting device.4 Remove the retaining fasteners from bothsecondary boom extend limit switches andremove the limit switches. Do not disconnectthe wiring.Note: Label the location of each limit switch as theyare not the same and their mounting locationscannot be exchanged.5 Tag, disconnect and plug all hydraulic hosesfor the 3 secondary boom extension cylinders.Cap the fittings on the cylinder.Bodily injury hazard. Sprayinghydraulic oil can penetrate andburn skin. Loosen hydraulicconnections very slowly to allowthe oil pressure to dissipategradually. Do not allow oil tosquirt or spray.6 Remove the upper extension cylinderretainers from the saddle blocks.
