October 2019 Service and Repair ManualBoom ComponentsPart No. 1280490GT S® -80 XC ™ • S® -85 XC ™ • S®-80 HF • S®-85 HF 474-4 Boom Extension C ylinder4-4Boom Extension CylinderThe boom extension cylinder is located inside theboom assembly and incorporates cables andpulleys that are responsible for extending thenumber 3 boom tube. The primary boom extensioncylinder is equipped with counterbalance valves toprevent movement in the event of a hydraulic linefailure.How to Remove the BoomExtension CylinderBodily 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 boom fullyretracted.1 Raise the boom to a horizontal position.2 Remove the boom end cover retainingfasteners and remove the cover.3 Remove the access covers from both sides ofthe boom at the pivot end.4 Remove the mounting plates and the stringpotentiometer.5 Fully loosen the lock nuts on the extendcables. Do not remove the nuts.1 boom angle sensor2 string potentiometer3 cable guard4 cable guard retaining plate6 Loosen the retract cable nut at the platformend of the boom. Pull the cable rod from thesupport and let it hang down.7 Remove the cable guard fasteners andremove the cable guard.8 Locate the retaining plates that secure theretract cables to the inside of the number 3boom tube.9 Remove the cable retaining plates and pull theretract cables off of the pulleys. Lay the cablesflat and out of the way.
