FAQ

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• Wheel Bearing Adjustments
• Automatic Slack Adjusters

Automatic Slack Adjusters

October 1994 FMVSS 105 and 121 required that all new air-braked vehicles with S-Cam style brakes shall be equipped with automatic slack adjusters.

Well-known manufacturers of automatic slack adjusters: Bendix, Gunite, Crewson-Brunner, Haldex (SAB), and Meritor (Rockwell).

Adjustment: Bendix, Gunite, Crewson & Brunner and Haldex all can be adjusted in a similar manner. Turning the adjusting nut clockwise shortens the stroke (tightens up the brake). Turning the adjusting nut counter-clockwise adds stroke (loosens up the brake). You will find it will take about 20 to 25-ft. lb. of torque to back off the adjusting hex. On the other hand, if it backs off too easily, the auto slack needs replacement. Meritor automatic slack adjusters are slightly different. They require you to remove a pawl assembly to back them off on the earlier auto slacks, and the current units just require you to pry up a button on the pawl's cap to release the pawl.

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Lubrication
Yes, automatic slack adjusters need to be greased. But, you can over do it. Use a grease gun to lubricate automatic slack adjusters. Apply grease until the grease starts to purge out from around the camshaft or some type of grease relief. Be sure and inspect the seals and dust boots for damage after lubrication. Using the recommended lubricant is critical so you don't damage the internal clutch mechanism. Too heavy of grease can cause the automatic slack adjuster to back off on its own.

Replacement
You must use the same brand of automatic slack adjuster on both sides of the axle and it is recommended to keep the same brand on the entire truck. Each brand has subtle differences and should not be mixed on an axle.       ^TOP