Slack adjuster maintenance

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Mack offers the following maintenance and lubrication recommendations for Gunite automatic slack adjusters on LEU, MRU, GU, CHU and CXU vehicles.

Every three months or 25,000 miles:

• Check the condition of the foundation brakes, including drums, shoes, linings, cams, rollers, bushing, etc.

• Check for structural damage to the housing, worn clevis, worn clevis bushings and the boot for cuts or tears. Replace if necessary.

After allowing the brake drum to cool to room temperature, check for correct chamber stroke. Because of the variety of vehicle operating conditions, you may need to perform chamber stroke tests at earlier intervals.

Gunite automatic slack adjusters are factory lubricated and sealed to protect against dirt, water, salt and other corrosive elements. Nevertheless, periodic lubrication is recommended. Every six months or 50,000 miles, grease the slack adjuster using an approved grease.

The adjusters have a grease fitting to allow lubrication during normal chassis servicing. With a conventional grease gun, apply lubricant until grease appears on the camshaft or grease flows from the grease relief.

The current Gunite automatic slack adjusters are produced without a grease relief, forcing lubricant through the drilled worm wheel onto the camshaft. Previous designs incorporate a grease relief.

National Lubricating Grease Institute (NLGI) grade 1 and 2 greases without moly sulfides or EP additives having a working range of -40ºF to +120ºF are the recommended greases. Thick greases should be avoided.

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