SERVICE MANUAL(similar to that shown in Fig. 9) will be equipped with bushingswhich are serviceable. Replaced bushings are to have aclearance of .076-.127 mm (.003-.005 in.) between bushingand pin.CAMSHAFT, BUSHINGS AND SEALSThe camshaft is actuated by movement of slack adjuster. Therotating movement of cam forces shoe rollers away fromcam, thus forcing shoes into contact with drum.Removal procedure for camshaft assembly is covered in BrakeDisassembly procedure. When removing camshaft frombacking plate or spider, note position of spacing washers toassure correct reinstallation.Do not remove camshaft bushings from spider and/ormounting bracket unless replacement is necessary.Do not interchange right and left hand camshafts.Removal of brake chamber bracket will be required to replacethe bushings in some instances.To check bushings to determine if replacement is required,insert the camshaft in the bushing and check side play. Ifmore than .5080 mm (.020") on Wagner or Eaton brakes or.7620 mm (.030") on Rockwell brakes, the bushings needreplacing.Install new bushings with a suitable tool like that shown in Fig.21.Apply IH 251 HET grease or equivalent NLGI #2 multi-purposelithium grease to outside diameter of bushings to assist inpushing them into position.Fig. 21 Recommended Type of CamshaftBushing Removing ToolA Bushing Outside DiameterB Bushing Inside DiameterC Bushing lengthD Suitable LengthInstall new seals with lip of seal toward slack adjuster (Fig.22).Fig. 22 Brake Chamber Bracket Seal InstallationBRAKE CHAMBERSBrake chambers (Fig. 23) transform energy of compressed airinto mechanical force and motion to apply brakes. Onechamber is used at each wheel to operate brakes.Air pressure entering the brake chamber (Fig.23) behind the diaphragm forces the diaphragm and push rodoutward, rotating slack adjuster, brake camshaft and camapplying the brakes. The higher the air pressure admitted tochamber, the greater the force pushing brake shoes againstdrum.When air pressure is released from brake chamber, brakeshoe return springs and brake chamber release spring returnshoes, cam, slack adjuster and brake chamber back to thereleased position.The brake chamber consists of two dished metal sections;namely, pressure plate assebly and non-pressure plate,separated by a rubber diaphragm, all of which are heldtogether by a metal two-segment clamp. In front of thediaphragm are the push rod, push rod spring and retainer (Fig.23).Several types of spring actuated type parking brakes are usedin conjunction with or are attached to brake chambers whileothers replace the entire brake chamber.The purpose of auxiliary spring brakes is to provide anemergency brake which will stop the vehicle if air pressuredrops.These spring brake systems are covered in PARKING BRAKEsection of the Service Manual.Refer to the respective section pertaining toCTS-4080W - Page 15
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