Slack adjusters act as levers that increase the force of the air brake chambers. Their effective length is critical. Most slack adjusters are designed with two or three holes for attachment of the pushrod. Attaching the slack adjuster using a different hole changes the slack adjuster’s effective length. Make sure that the effective lengths of the slack adjusters on both sides of each axle (especially the steering axle) are the same. Also look for cracks and holes that are indicators of damage (not normal vent holes).