Specifications

17730-248 91 Component Replacement
AIRTEK
®
•
SOFTEK
®
for Blue Bird Buses
SERVICE HINT The easiest way to achieve this is with the grease caps not installed in the knuckle
assemblies. This eliminates back pressure. The assembly can then freely slide up and
down on the kingpin. If the grease caps are still installed, remove the grease zerks to avoid
creating back pressure. Grease zerks will be re-installed at the end of the procedure.
6. Install a bottle jack under the lower knuckle and slightly raise the knuckle until it is
possible to thread in the (3) brake backing plate bolts by hand. These are for guide
purposes only.
7. Snug the two socket head cap screws.
8. Lower the bottle jack so that all the vertical clearance is on the underside of the axle.
9. Affix a magnetic base dial indicator on the axle and place the tip of the dial indicator
on top of the knuckle assembly, see Figure 9-76.
10. Zero the dial indicator.
FIGURE 9-76
11. Raise the bottle jack until there is no
clearance between the knuckle
assembly and the bottom of the
axle, slightly lifting the axle.
12. Check the reading on the dial indi-
cator. The specification for vertical
travel on the steering knuckle during
assembly is 0.008" to 0.011".
13. If the clearance is above 0.011",
loosen the socket head cap screws
and push down on the knuckle
assembly until the proper vertical
clearance is achieved. Add (0.005") shim if necessary.
14. If the clearance is below the 0.008", loosen the two socket head cap screws and pull
up on the knuckle assembly until the proper vertical clearance is achieved. If the 0.008"
minimum clearance is unattainable it may be necessary to remove a 0.005" shim.
NOTE The Hendrickson Genuine part, socket head cap screw comes with a pre-applied loctite
compound.
PRIOR TO INSTALLATION ENSURE THAT ALL RESIDUAL LOCTITE MATERIAL IS REMOVED FROM
THE MOUNTING BOLTS AND THE THREAD BORES IN THE UPPER STEERING KNUCKLE, AND
NEW LOCTITE 277 OR EQUIVALENT IS APPLIED TO HELP ENSURE THAT THE BOLTS SUSTAIN
THE PROPER TORQUE REQUIREMENT. FAILURE TO DO SO CAN CAUSE LOSS OF VEHICLE
CONTROL RESULTING IN PERSONAL INJURY OR PROPERTY DAMAGE.
15. Remove one old socket head cap screw and replace with new socket head cap screw.
16. Remove second socket head cap screw and replace with new socket head cap screw.
Tighten both socket head cap screws to 175-200 foot pounds torque.
17. Recheck the vertical clearance with the dial indicator or a 0.010" feeler gauge, see
Figure 9-76.
18. Remove the brake spider bolts, they should thread out freely.
19. Remove the bottle jack and continue assembling the wheel ends.
IMPORTANT NOTE Loctite applied to the three brake spider bolts is a critical procedure to ensure that these
bolts sustain the torque requirement of Steering knuckle assembly.
SERVICE MANUAL
L
133
FRONT AXLE & SUSPENSION
1
APPENDIX