Keeping Suspensions Working For You

The critical aspect is having components function properly together.


• Top pad and rubber axle stop: Look for cracks and/or missing rubber axle stops. The rubber axle stop is exposed to contact forces in extreme jounce conditions. It will be necessary to visually inspect the rubber axle stop for wear at the specified inspection interval.

• Torque box (equipped on Hendrickson HTB suspensions): Inspect the torque box for cracks, damage, torn or shredded rubber or any signs of looseness at the bar pin clamps. Replace all worn or damaged parts. The torque box is a non-serviceable item and must be replaced as an assembly if damaged, or if the bushings are worn out.

• Torque rods: All torque rods must be inspected for looseness, torn or shredded rubber, bushing walk-out and proper fastener torque. If there is metal-to-metal contact in the bushing joint, this is a sign of excessive bushing wear and the bushing needs to be replaced.

FRONT SUSPENSION

Here again, Hendrickson recommends a periodic visual inspection, per the manufacturer's specification, plus checking for the following:

• Tire wear: Inspect tires for wear patterns that may indicate suspension damage or misalignment. The leading causes of tire wear are, in order of importance: tire pressure, toe setting, thrust angle and camber.

• Wear and damage: Inspect all parts of suspension for wear and damage. Look for bent or cracked parts. Replace all worn or damaged parts.

• Fasteners: Look for any loose or damaged fasteners on the entire suspension. Make sure all fasteners are tightened to the specified torque. Use a calibrated torque wrench to check torque in a tightening direction. Correct the torque if necessary. Replace any worn or damaged fasteners.

• Steel leaf spring: Look for cracks. Replace if cracked or broken. Check the front bushing for any wear or deterioration. Replace if necessary.

• Air spring (if equipped): Look for chaffing or any signs of spring or component damage.

• Front and rear spring hangers: Check for excessive movement. Check for cracks or loose mounting hardware and replace if necessary.

• Thrust washers and rear hanger clamp: Look for any signs of excessive wear to the thrust washers and rear hanger clamp.

• Rear spring mount: Check for proper alignment with spring taper and check for proper torque on rear spring mount fasteners.

• Shocks: Look for any signs of dents or leakage. Misting is not considered a leak.

• Clamp group: Check torque on clamp group mounting hardware. Refer to the manufacturer's torque specifications.

• Top and bottom axle wrap liners: Look for any cracking or broken pieces on liners.

• Axle: The axle should be free of any nicks or gouges. Inspect for any cracks or dents.

• Steering pivot points: Check for looseness at all pivot points.

• Operation: All steering components must move freely through the full range of motion from axle stop to axle stop.

RECOMMENDED MAINTENANCE

Preventative maintenance for front and rear suspensions should include the following, counsels Hendrickson.

• Fasteners: Look for any loose or damaged fasteners on the entire suspension and axle assembly. Check for any component slippage or weeping rust trails. Make sure all fasteners are at required torque. Replace any worn or damaged fasteners.

• Shock absorbers: Check all mounting hardware for correct torque. Inspect for leaks. Fluid streaming from the upper seal is a leaking shock and needs to be replaced (misting is not considered a leak). Perform heat test. Check for internal failure. Check for damage, which could include damaged upper or lower mount, damaged upper or lower bushing, damaged dust cover and/or shock body, bent or dented shock and improper installation.

• Clamp group (U-bolt/hex bolt): Clamp group should be properly aligned and bolts properly seated. Re-torque clamp group locknuts periodically per the manufacturer's recommendation. If signs of movement are present, disassemble the clamp group. Inspect for component wear or damage and replace as necessary.

• Ride height checking procedure (air suspensions only): Ride height setting - measured from the bottom of the upper air spring bracket to the bottom of the air spring piston flange - will vary between suspension models. (Ride height gauges are available for most Hendrickson air suspensions.): Ride height front and rear must be correctly set prior to checking vehicle alignment.

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