On-highway — every 10,000 miles (16,000 km) or 6 months, whichever comes first.

COMPONENT INSPECTION
■■

Clamp group — Check torque on clamp group mounting hardware. Refer to the Clamp Group
Re-Torque Interval in this section.

■■

Top pad — Check for cracks or damage. Replace if ­n ecessary, see the Component
Replacement Section of this publication for replacement procedure.

■■

Fasteners — Look for any loose or damaged fasteners on the entire suspension. Make sure all
fasteners are tightened to the specified torque, see Torque Specification Section of this publication for recommended torque requirements. Use a calibrated torque wrench to check torque
in a tightening direction. As soon as the fastener starts to move, record the torque. Correct the
torque if necessary. Replace any worn or damaged ­fasteners.

■■

Shock absorber — Look for any signs of dents or leakage. Refer to the Shock Absorber
Inspection in this section.

■■

Leaf spring assembly — Look for cracks. Check the front and rear bushings for any wear
or deterioration. Replace spring assembly as necessary. See the Component Replacement
Section of this publication for replacement procedure.

■■

Air spring — Look for chaffing or any signs of spring or component d­ amage.

■■

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

■■

Steering pivot points — Check for looseness at all pivot points. Inspect and lubricate all pivot
points, maximum service interval is 10,000 miles. Refer to Lubrication Intervals, Table 7-1
STEERTEK NXT Greasing and Lubrication Specifications in this section.

■■

STEERTEK NXT Axle and Tie Rods — The axle should be free of any nicks or gouges. Inspect
for any cracks or dents on axle, replace as necessary. Refer to Lubrication and Tie Rod Ends
Inspection in this section.

■■

Tire wear — Inspect tires for wear patterns that may indicate suspension damage or misalignment. See Tire Inspection in this section.

■■

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

See vehicle manufacturer’s applicable publications for other preventive maintenance
requirements.

17730-313

15

Towing Procedure

AIRTEK® for Hoist Liftruck T-Series
LUBRICATION INTERVALS
For vehicles equipped with the STEERTEK NXT axle, regular lubrication intervals should be ­followed to
help prevent premature wear to the kingpin bushings and tie rod ends, see lubrication chart below.
NOTE

The recommended service lubrication interval is a guideline, the vehicle may require increased
lubrication interval depending on severity of operation.

TABLE 7-1

STEERTEK NXT Greasing and Lubrication Specifications
COMPONENT
KINGPIN
BUSHINGS

GREASING INTERVAL

TIE ROD ENDS

Maximum of 10,000 miles
(16,100 kilometers), or 90
days, whichever comes first.

DRAG LINK

See Vehicle Manufacturer

GREASE
Multipurpose
Grease

NLGI
GRADE
2

OUTSIDE TEMPERATURE
Refer to the lubricant manufacturer’s
specifications for the temperature
service limits applicable to your area.

NOTE: Lubrication greases acceptable for use on the STEERTEK NXT axle will carry a designation of NLGI #2 EP and rated
GC-LB or equivalent.

KINGPIN LUBRICATION

FIGURE 7-1

STEERTEK NXT upper kingpin grease zerks are
located on the inboard side of the steering knuckle
and upper kingpin connection, see Figure 7-1. On
some models of the STEERTEK NXT a grease zerk is
located on the bottom of lower steering knuckle on
the inboard side.

Upper
Grease Zerk

1. Place vehicle on the ground.
2. Prior to greasing the kingpins on the vehicle,
the suspension must be in a loaded c­ ondition.
3. Clean off all the grease zerks and grease gun tip with a clean shop towel prior to l­ubrication.
4. Lubricate the kingpins through the grease zerks on the top and bottom of the steering knuckle,
see Lubrication Specification Table 7-1 above.
5. Force the required lubricant into the upper and lower kingpin grease zerks, until new lubricant
flows out from the upper kingpin connection and steering knuckle and the thrust bearing
purge locations, see Figures 7-2 and 7-3.
FIGURE 7-2

Preventive Maintenance

FIGURE 7-3

16

17730-313

AIRTEK® for Hoist Liftruck T-Series
FIGURE 7-4

NOTE

Greasing at the lower zerk should
purge grease from the thrust bearing shell. The left side of the axle has a
composite style thrust bearing and the
right side of the axle has a steel roller
thrust bearing, see Figure 7-4. Both
purge in the same area.

Black Seal

TIE ROD END LUBRICATION

Top View of Thrust Bearings
Seal

COMPOSITE Left Side

ROLLER Right Side

LUBRICATION PROCEDURE
1. Turn the vehicle wheels straight ahead.
2. Wipe the grease zerk and grease gun tip with clean shop towels.
3. Wipe the seal / boot clean with shop towels.
4. Attach a grease gun to the grease zerk. Either a hand or pneumatic grease gun is acceptable.
If air operated grease gun is used, system air pressure should not exceed 150 psi (1035 kPa).
FIGURE 7-5

EXCEEDING THE MAXIMUM AIR PRESSURE TO THE GREASE
ZERK CAN CAUSE DAMAGE TO THE DUST BOOT CAUSING
COMPONENT FAILURE.

5. Dirt, water, and discolored old grease should flow from
the relief vents or purge holes near the boot crimp or
bellows area, see Figure 7-5. Continue to purge grease
until fresh grease flows from the purge area.

Dust Boot

6. If the tie rod end is designed for lube service and it
will not accept grease proceed as follows:
Boot Crimp

a. Remove the grease zerk.
b. Inspect the threaded grease zerk hole in the tie
rod end and remove any obstructions.

Zerk Fitting

c. Install a new grease zerk.
d. Continue the lubrication procedure.
e. If the tie rod end will not accept grease following this procedure it will be necessary to
replace the tie rod end. Refer to Tie Rod Ends in Component Replacement Section of this
publication.
7. Apply grease until all the old grease is purged from the boot and fresh grease is coming out.

TIE ROD ENDS
INSPECTION
Before beginning this inspection procedure, the entire system must be unloaded (i.e., the front
end of the vehicle must be raised and supported with safety stands).
DO NOT GREASE THE TIE ROD ASSEMBLY BEFORE PERFORMING THE INSPECTION. DOING SO CAN
INHIBIT EFFORTS TO DETERMINE ACTUAL WEAR.
REPLACE THE ENTIRE TIE ROD END IF THE BOOT IS TORN OR MISSING, FAILURE TO DO SO CAN CAUSE
PREMATURE WEAR OF THE TIE ROD END.

17730-313

17

Preventive Maintenance

AIRTEK® for Hoist Liftruck T-Series
1. Block rear wheels of vehicle. Using the bottom of the axle beam or the frame rails, raise the
front end off the ground and support with stands.
2. With the engine off, turn the wheels from full left to full right and then return to the straightahead position.
3. Check that the boots are in place and completely installed over the tie rod ends.
4. Check for cracking or tears in the boots. Also check the boot seals for damage. Replace the
entire tie rod end if the boot is damaged.
THE COTTER PIN MUST BE INSTALLED CORRECTLY THROUGH THE TIE ROD END WITH THE CASTLE NUT
TIGHTENED TO THE PROPER TORQUE SPECIFICATION IN ORDER TO SECURELY ATTACH THE TIE ROD.
LOSS OF THE COTTER PIN CAN CAUSE THE TIE ROD END NUT TO BECOME LOOSE AND ADVERSELY
AFFECT VEHICLE STEERING AND POSSIBLY RESULT IN TOTAL LOSS OF STEERING CONTROL.

5. Check that the tie rod end nut is installed and secured with a cotter pin. If the cotter pin is missing, check the nut torque specification and then install a new cotter pin. Always tighten the castle
nut to specified torque when setting the cotter pin. DO NOT back off the nut to insert cotter pin.
IT IS CRITICAL TO CHECK THE 5⁄ 8" TIE ROD CLAMP BOLT HEAD LOCATION TO VERIFY THE CLAMP
FASTENERS HAVE SUFFICIENT CLEARANCE AWAY FROM THE LOWER SHOCK MOUNT AT FULL WHEEL
CUT. THE FASTENERS MUST NOT CONTACT THE LOWER SHOCK MOUNT. FAILURE TO DO SO CAN
CAUSE ONE OR MORE COMPONENTS TO FAIL CAUSING LOSS OF VEHICLE CONTROL AND POSSIBLE
PERSONAL INJURY OR PROPERTY DAMAGE.

6. Verify the 5⁄8" tie rod clamp bolt head does not contact the lower shock mount at full wheel
cut, see Figure 7-6.
THE THREADED PORTION OF THE TIE ROD END MUST EXTEND PAST THE SLOTS INTO THE TIE ROD
CROSS TUBE, SEE FIGURE 7-6. FAILURE TO DO SO CAN CAUSE COMPONENT DAMAGE, LOSS OF
VEHICLE CONTROL AND POSSIBLE PERSONAL INJURY OR PROPERTY DAMAGE.

7. Check that the tie rod end is threaded correctly into the cross tube and is engaged deeper
than the end of the cross tube slot. The tie rod end must be visible the entire length of the
cross tube slot, see Figure 7‑6.
8. Check that grease zerks are installed. Replace a damaged grease zerk with a new one.
FIGURE 7-6
5/8"

Tie Rod Clamp Bolt
It is critical to check the 5/8" tie rod clamp bolt head
location to verify the clamp fasteners have sufficient
clearance away from the lower shock mount at full wheel
cut. The fasteners must not contact the lower shock mount.
Tie Rod Cross Tube Slots
It is critical to have the threaded portion of the tie rod
end extend past the slots in the tie rod cross tube.
5/8" Tie

Rod Clamp Locknut
Tightening Torque
68 ± 7 ft. lbs. (92 ± 9 Nm)

Threaded Portion
of the Tie Rod End

DO NOT USE THE FOLLOWING ITEMS OR METHODS TO CHECK FOR MOVEMENT OF THE TIE ROD
ASSEMBLY, WHICH CAN CAUSE DAMAGE TO COMPONENTS:
■■

A CROW BAR, PICKLE FORK OR 2 X 4

■■

ANYTHING OTHER THAN HANDS USED TO GRASP AND ROTATE THE CROSS TUBE ASSEMBLY (CAN
RESULT IN DAMAGE TO THE CROSS TUBE)

■■

EXCESSIVE PRESSURE OR FORCE APPLIED TO THE TIE ROD ENDS OR THE JOINTS OF THE ASSEMBLY

9. By hand or using a pipe wrench, with jaw protectors to avoid gouging the cross tube, rotate the
cross tube toward the front of the vehicle and then toward the rear. After rotating, center the cross
tube. If the cross tube will not rotate in either direction, replace both tie rod ends, see Figure 7-7.
Preventive Maintenance

18

17730-313

AIRTEK® for Hoist Liftruck T-Series
FIGURE 7-7

FIGURE 7-8

FIGURE 7-9

10. Position yourself directly below the tie rod end.
Using both hands, grab the assembly end as
close to the tie rod end as possible (no more
than 6" or 152.4 mm). Apply hand pressure
with reasonable human effort vertically up
and down in a push-pull motion several times,
using approximately 75 ± 25 foot pounds (102
± 34 Nm) of force. Check for any movement
or looseness at both tie rod end locations, see
Figure 7-8.
11. If there is any movement in the tie rod assembly,
install a magnetic based dial indicator on the
Ackermann arm, see Figure 7-9.
12. Set the dial indicator to zero.
13. Apply hand pressure with reasonable human effort vertically up and down in a push-pull
motion several times, using approximately 75 ± 25 foot pounds (102 ± 34 Nm) of force.
Observe the reading on the dial indicator.
14. If the reading is more than 0.060", replace both tie rod ends at the next service i­nterval.
15. If a tie rod end exhibits ≥ 0.125" of movement by hand, the vehicle should be removed immediately from use and replace the tie rod end.
NOTE

According to the Commercial Vehicle Safety Alliance (CVSA), the “out of service” criteria for front
steer axle tie rod assemblies on any commercial vehicle is: Any motion other than rotational
between any linkage member and its attachment point of more than 1⁄8" (3 mm) measured with
hand pressure only. (393.209(d)), (published in the North American Standard Out-of-Service
Criteria Handbook, April 1, 2006.)

CLAMP GROUP RE-TORQUE INTERVAL
1. Clamp group locknuts must be torqued to specification at preparation for delivery.
2. Clamp group locknuts must be re-torqued at 1,000 miles (1,609 km).
LOOSE OR OVER TORQUED FASTENERS CAN CAUSE COMPONENT DAMAGE, LOSS OF VEHICLE
CONTROL, PROPERTY DAMAGE, OR SEVERE PERSONAL INJURY. MAINTAIN CORRECT TORQUE VALUES
AT ALL TIMES. CHECK TORQUE VALUES ON A REGULAR BASIS AS SPECIFIED.

3. Thereafter follow the 6 month / 25,000 miles (40,000 km) visual inspection and annual retorque interval.

17730-313

19

Preventive Maintenance

AIRTEK® for Hoist Liftruck T-Series
FIGURE 7-10

FIGURE 7-11

4. Ensure that the clamp group is properly aligned and the U-bolts / hex bolts are seated in the
top pad, and the top pad / bottom axle wrap is centered on the axle spring seat / top axle
wrap, see Figure 7-10 and 7-11.
5. Check for the signs of component or bolt movement.

FIGURE 7-12

6. If signs of movement are present, disassemble the clamp group fasteners, check for component wear or damage and replace as necessary,
then install new clamp group fasteners and repeat Steps 1 through 5.
7. Tighten the clamp group locknuts evenly in 50 foot pounds increments
in the proper pattern, see Figure 7‑12, to achieve uniform bolt tension to
300 ± 10 foot pounds torque.

SHOCK ABSORBERS
NOTE

It is not necessary to replace shock absorbers in pairs if one (1) shock absorber requires
replacement.
FIGURE 7-13

Hendrickson uses a long service life, premium shock absorber
on all AIRTEK suspensions. When the shock absorber replacement is necessary, Hendrickson recommends that the shock
absorbers be replaced with identical Hendrickson Genuine
parts for servicing. Failure to do so will affect the suspension
performance, durability, and will void the w
­ arranty.
Inspection of the shock absorber can be performed by doing
a heat test, and a visual inspection. For instructions on shock
absorber replacement see the Component Replacement Section
of this publication. It is not necessary to replace shock absorbers
in pairs if one (1) shock absorber requires replacement.

HEAT TEST
1. Drive the vehicle at moderate speeds on rough road for
minimum of fifteen minutes.
DO NOT GRAB THE SHOCK AS IT COULD POSSIBLY BE HOT AND
CAUSE PERSONAL INJURY.

2. Lightly touch the shock body carefully below the dust cover,
see Figure 7-13.
3. Touch the frame to get an ambient reference. A warm shock absorber is acceptable, a cold
shock absorber should be replaced.
Preventive Maintenance

20

17730-313

AIRTEK® for Hoist Liftruck T-Series
4. To inspect for an internal failure, remove and shake the suspected shock. Listen for the sound
of metal parts rattling inside. Rattling of metal parts can indicate that the shock has an internal failure.

VISUAL INSPECTION
Look for these potential problems when doing a visual inspection. Inspect the shock absorbers
fully extended. Replace as necessary.
FIGURE 7-14

SHOCK ABSORBER VISUAL INSPECTION - UNACCEPTABLE CONDITIONS

LEAKING VS. MISTING SHOCK VISUAL INSPECTION
FIGURE 7-15

The inspection must not be conducted after driving
in wet weather or a vehicle wash. The shock absorber
needs to be free from water. Many shock absorbers are
often misdiagnosed as failures. Misting is the process
whereby very small amounts of shock absorber fluid
evaporate at a high ­o perating temperature through
the upper seal of the shock absorber. When the “mist”
reaches the cooler outside air, it condenses and forms a
film on the outside of the shock absorber body. Misting
is perfectly normal and necessary function of the shock
absorber. The fluid which evaporates through the seal
area helps to lubricate and prolong the life of the seal.
A shock absorber that is truly leaking and needs to be
replaced will show signs of fluid leaking in streams
from the upper seal. These streams can easily be seen
when the shock absorber is fully extended, underneath the main body (dust cover) of the shock
absorber. Look for these potential problems when doing a visual inspection. Inspect the shock
absorbers fully extended. Replace as necessary.
NOTE

The AIRTEK suspension is equipped with a premium seal on the shock absorber, however this seal
will allow for misting to appear on the shock absorber body (misting is not a leak and is considered acceptable).
Inspect the shock absorber fully extended. A shock absorber that is truly leaking will show signs
of fluid leaking in streams from the upper seal. These streams can easily be seen, underneath
the main body (dust cover) of the shock absorber. Replace as necessary.

17730-313

21

Preventive Maintenance

AIRTEK® for Hoist Liftruck T-Series
STEERING KNUCKLE
CHECKING VERTICAL END PLAY (UP AND DOWN MOVEMENT)
The operating spec for vertical clearance on the steering knuckle is 0.008" to 0.030".
FIGURE 7-16

1. Chock the rear tires to help prevent the vehicle
from moving.
2. Set the parking brakes.
3. Use a jack to raise the vehicle until both tires are
1" off the ground.

Ensure the tip of the
dial indicator is on
the top of the upper
steering knuckle and
not on the grease cap

4. Place a dial indicator on each side of the axle
as follows:
a. Index the wheels slightly (left or right).
b. Place the magnetic dial indicator base on the
axle, see Figure 7-16.
c. Place the tip of the dial indicator on the top
of the upper steering knuckle (not on the
grease cap).
5. Set the dial indicator to “0” (zero).
6. Lower the jack.
7. If vertical end play is greater than 0.030" or below 0.008", an adjustment of the upper knuckle
is necessary. If the vertical end play is:
■■

Greater than 0.030", loosen the socket head cap screws and push down on the knuckle
assembly until the proper vertical end play is achieved.

■■

Less than 0.008", loosen the socket head cap screws and pull up on the knuckle assembly until the proper vertical end play is achieved.

8. Retighten the socket head cap screws to

188 ± 12 foot pounds (255 ± 16 Nm) torque.

KINGPIN BUSHING WEAR
CHECKING STEERING KNUCKLE LATERAL MOVEMENT
NOTE

Preventive Maintenance

If one (1) bushing is worn or damaged, it is mandatory to replace both the top and bottom bushings on that knuckle assembly.
FIGURE 7-17

FIGURE 7-18

CHECKING UPPER KINGPIN BUSHING

CHECKING LOWER KINGPIN BUSHING

22

17730-313

AIRTEK® for Hoist Liftruck T-Series
FIGURE 7-19

1. Chock the wheels to help prevent the vehicle
from moving. Set the parking brake.
2. Use a jack to raise the vehicle until the
wheels are off the ground. Support the vehicle with safety stands.
3. CHECKING THE UPPER KINGPIN BUSHING.
Install the base of a dial i­ndicator onto the
axle beam and face the tip against the steering knuckle, see Figure 7-17.
4. Set the dial indicator to “0” zero.
5. Move the top of the tire in and out by applying reasonable constant pressure and then
release, see Figure 7-19.
6. Check the reading on the dial indicator. If the
dial indicator moves more than 0.015", the
upper bushing is worn or damaged. Replace
both bushings. Refer to the Kingpin Bushing
replacement procedure in the Component
Replacement Section of this publication.
7. CHECKING THE LOWER KINGPIN BUSHING. Install a dial indicator so that the base is on the
axle and the indicator tip is against the inside of the bottom of the knuckle, see Figure 7‑18.
8. Set the dial indicator to “0” zero.
9. Move the bottom of the tire in and out. If the dial indicator moves more than 0.015", the
lower bushing is worn or damaged. Replace both kingpin bushings. Refer to the Component
Replacement Section of this publication.

TIRE INSPECTION
The leading causes of tire wear are the following, in order of importance:
1. Tire Pressure
2. Toe Setting
3. Thrust Angle
4. Camber
The following tire Inspection guidelines are based upon Technology & Maintenance Council
(TMC) recommended practices. Any issues regarding irregular tire wear where Hendrickson is
asked for assistance, will require tire and alignment maintenance records, reference TMC’s literature numbers RP 219A, RP 230, or RP 642.
Tire wear is normally the best indicator of vehicle alignment condition. If tires are wearing too rapidly or irregularly, alignment corrections may be needed. The tire wear patterns described below
can help isolate specific alignment problems.