Keeping Suspensions Working For You

The critical aspect is having components function properly together.


• Lubrication: Do periodic lubrication per the manufacturer's recommendations. Adjust the grease interval to accommodate application and environment. Use multipurpose grease. Refer to lubricant manufacturer's specifications for temperature service limits applicable to your area. Grease component until a clean grease purge is observed.

For front suspensions, Hendrickson says there also needs to be preventative maintenance on the steering knuckle thrust bearings, of which there are two different designs: composite bearing installed on left side, and roller bearing installed on the right side. For these, the lubrication must be performed with the axle in the loaded condition. Clean all grease zerks and the grease gun tip before applying grease. Fresh grease must purge on both thrust bearings

FRONT INSPECTION

The inspection procedure for front suspensions also consists of the following steps, says Hendrickson.

• Tie rod ends:
Nut - Verify that it is tight and the cotter pin is in place. If loose, remove and inspect mating parts. If no damage is found, re-install and torque to specs, and install a new cotter pin.
Seal - It must be free of tears and cracks. Replace the tie rod end if any damage is found. Boots must be in place and installed over the tie rod ends.
Zerk - Verify proper installation. If damaged or missing, replace the tie rod end.

• Tube/end connection: Check for loose tube/end connections. Replace either end. If loose, replace the assembly.

• Tube and clamps: Check for road damage and replace if damage is found. Check the clamps and replace if damaged or loose. Position the clamps so they don't interfere with the axle.

• Slot: Verify that the tie rod end is installed deeper than the slot. If the slot is open, replace the tie rod end with proper length.

• Tie rod rotation: Block rear wheels of vehicle and raise the front end off the ground and support with stands. With the engine must off, turn the wheels from full left to full right and return to the straight-ahead position. Rotate the cross tube by hand, or with a jaw protected pipe wrench, toward the front and then toward the rear and center cross tube. If the cross tube will not rotate in either direction, replace both tie rod ends.

• Vertical tie rod end play: Apply approximately 100 pounds of hand force in a push/pull type action to the underside of the tube near the tie rod end. Use hand pressure only, no prybars. If endplay is observed, recheck using a dial indicator. Note: Tie rod ends must always be replaced in pairs, and always grease tie rod ends following an inspection.

• Thrust washers: Inspect for excessive wear at regular inspection intervals. Look for excessive side-to-side movement of the spring or suspension. Check spring taper for contact with the rear hanger. Minimum allowable thickness of thrust washer will vary by suspension model. Replace in sets if worn on one side. Inspect rear hanger or shackle for damage

To inspect the king pin busing, Hendrickson says unload axle. Move the top of the tire in and out by applying reasonable constant pressure, then release. If movement is felt, apply the service brake and repeat. If movement is still present, install a dial indicator on the knuckle and repeat. Movement of more than 0.015 inches indicates worn king pin bushings.

King pin bushings preventative maintenance involves inspection with a dial indicator. Attach it to the axle and zero the indicator. Move the top of tire in and out by hand. A reading of more than 0.015 inches requires bushing replacement. If the upper bushing is within spec, then typically the lower is within spec. Both bushings must be replaced in sets.

As part of the preventive maintenance for the Hendrickson SteerTek front axle suspensions, which have axle wrap liners to prevent any type of abrasion at the axle clamp area, the liner should be replaced any time the axle wrap is removed. If the liner is cracked and all the pieces are intact, it is not necessary to replace the liner. If the liner is broken out and there are pieces missing, the liner must be replaced immediately.

LIFT AXLES

For lift axles, Hendrickson recommends a monthly inspection of shock absorbers for leaks and coil spring integrity where applicable, as well as a monthly general overview-type inspection of axle and suspension components. Every three months, king pin bushings and tie rod end connections should be greased. An inspection of toe setting on the axles should be conducted every six months.

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