INSTRUCTION TO SERVICE
ITS: 6696
SECTION:

204

WRITTEN BY:

Michael Rooney

SUBJECT:

HY-1336 to HY-1350 Rear Axle Conversion.

Rear Suspension

ITS6696

THIS DOCUMENT AND THE CONTENTS DISCUSSED HEREIN ARE THE CONFIDENTIAL AND
PROPRIETARY INFORMATION OF NEW FLYER INDUSTRIES CANADA ULC AND NEW FLYER OF
AMERICA INC. AND ARE DISCLOSED BY NEW FLYER IN CONFIDENCE. THIS DOCUMENT AND THE
CONTENTS HEREIN ARE NOT TO BE DISCLOSED BY THE INTENDED RECIPIENT WITHOUT THE PRIOR
WRITTEN AUTHORIZATION OF NEW FLYER. ANY UNAUTHOIZED DISCLOSURE, REPRODUCTION OR
OTHER DISTRIBUTION OF THIS DOCUMENT OR INFORMATION IS STRICTLY PROHIBITED AND MAY
RESULT IN ACTION BEING TAKEN AGAINST THE PARTY MAKING THE UNAUTHORIZED DISCLOSURE.
THIS DOCUMENT AND ALL COPIES HEREOF MUST BE RETURNED TO NEW FLYER UPON REQUEST.

PROCEDURE:
Rear Axle Removal
1. Turn the main battery disconnect switch to the “OFF” position.
2. Drain the air from all the air tanks using the procedure in the Service Manual.
3. Raise coach in accordance with the New Flyer Service Manual and support with jack stands.
4. Using wheel lifts, support the weight of the rear axle and cradle assembly. Lower the rear wheel lifts slightly to
allow the axle assembly to drop approximately 3”.
5. Disconnect the levelling valve linkages at the ends of the leveling valve arm on each side of the rear suspension,
do not disturb adjustment. Pull the valve lever down to drain air from the air springs.
6. Locate the air-lines that run from the brake valve mounting plate to the rear brakes.
a.

Mark and disconnect the two air-lines that attach to the Relay Valve then tape the ends of the air-lines to
prevent dirt entry.

b.

Mark and disconnect the two air-lines that attach to the Quick Release Valve then tape the ends of the airlines to prevent dirt entry.

Lower Shock Absorber Mounts

Levelling Valve Link
Levelling Valve Link
Relay Valve Air Lines

Quick Release Valve
Air Lines

Figure 1: Air Line & Levelling Link Disconnection Points.

7. Unplug the ABS sensor harness pigtails at the points where they connect to the vehicle wire harness.
8. Unplug the brake wear sensor harness from the vehicle wire harness if equipped.

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9. Remove the breather membrane and the bracket attached to the vehicle structure.
10. Disconnect the drive shaft:
a.

Mark the drive shaft with reference marks across the splines so that the yoke can be re-installed in the
same orientation later.

b.

Remove the four bolts that attach the driveshaft to the differential and discard them.

c.

Slide the yoke assembly off the driveshaft and set it aside.

11. Remove the nuts that attach the four air bags to the suspension cradle. Set the bolts aside for re-use. The air
bags will remain with the bus when the suspension is lowered.
12. Remove the hardware that attaches the lower ends of the four shock absorbers to the suspension cradle. Set
the hardware aside for re-use. The shock absorbers will remain with the bus when the suspension is lowered.
13. Disconnect the upper and lower radius rods at their chassis mounting points but leave the opposite ends
attached to the differential unit. Set aside the mounting hardware for reuse.
14. Carefully lower the axle and suspension cradle assembly to the floor with the wheel lift.
WARNING: Make sure the assembly is strapped or chained to the lifting device to prevent it from
tilting or falling.

Axle Change Over.
15. Support the rear suspension unit on jack stands or suitable work stand.
16. Remove the wheel and tire assemblies from the axle.
17. Remove the brake chambers using the following steps:
a.

Mark the air-lines that attach to the brake chambers and disconnect them from the brake chambers. Cover
the ends of the air-lines with tape to prevent dirt intrusion.

b.

Release and cage the spring brake by rotating the brake chamber release bolt counter-clockwise
approximately 22 to 23 turns. The force to compress the spring must not exceed 74 ft-lb (100 Nm) during
the caging process. The brake chamber is considered fully caged when the head of the release bolt
extends approximately 1.30” beyond the surface of the brake chamber.
NOTE: For easier turning of the release bolt, apply 95 to 125 psi shop air pressure to the air inlet marked
“Spring”. After caging, completely exhaust air from the spring chamber.
CAUTION: DO NOT use impact tools to cage or uncage the brake chamber.

c.

Remove the two 16 MM lock nuts securing the brake chamber to the brake caliper assembly and remove
the brake chamber from the vehicle.

d.

Cover the brake chamber openings and clean the brake chamber mounting surfaces.

e.

Place a protective cover over the brake caliper to prevent entry of contaminents.

18. Disconnect the brake drag sensors at either caliper.
19. Disconnect the ABS sensors at either wheel.
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20. Remove nuts, spacers and jacking pad assembly from the four U-bolts that retain the axle tube to the
suspension cradle. Inspect the spacers for corrosion damage, if they are in good condition they may be reused.

NOTE: Due to corrosion it may be necessary to heat the nuts that retain the U-bolts or cut the Ubolts. Sealant has been applied to the U-bolts stiffener plates and spacer tubes during the
installation process. It may be necessary to pry mounting hardware pieces to release and
fully remove them.

U-Bolts

Spacers

Washer
Jacking Pad
Locknut

Figure 2: U-Bolts & Hardware.
21. Use hoisting equipment with a minimum of 10,000 lb. (4,550 kg) to lift the axle assembly off the cradle and
onto an axle stand equipped to prevent the axle from rotating when set in place. If necessary, tie the axle to
the stand with chains or straps.
22. Lift the new HY-1350 axle assembly NF P/N 559392 onto the suspension cradle.
a.

Install new U-bolts NF P/N 440517 (two per side), Spacers NF P/N 334596 (if required) and the stiffener
plates and jacking pads removed earlier.

b.

Coat the threads on the U-bolts with Never Seez® NF P/N 5928660 and install new washers NF P/N
20W14000 and lock nuts NF P/N 504779. Torque the nuts initially to 50 ft-lb. (68 Nm).

c.

Working in a circular pattern from inner to outer bolts, torque bolts in increments of 100 ft-lb. (135 Nm)
until 380 ft-lb. (515 Nm) is achieved.

d.

Apply Sikaflex 221 NF P/N 242702 to the edges of the spacer tubes and the stiffener plates to ensure a
seal between the top and bottom plates. Also seal the U-bolt to the top plate holes in the suspension
beam.

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23. Install the brake chambers removed from the old axle on the new axle assembly:
CAUTION: Disc brake chambers must be inspected for seal condition and height
measurement before a used brake chamber can be reinstalled.
a.

Measure the height of the seal on the brake chamber. The seal must be in good condition and protrude
at least 0.118” (3.0 mm) from the brake chamber mounting surface. If the seal measures less than 0.118”
(3.0 mm) then the brake chamber must be replaced as an assembly.

b.

Check that the brake chamber mounting surface and brake caliper surface are clean, then remove
protective covers over the openings on both components.

c.

Apply Renolit Unitemp 2 grease to the spherical cup located in the brake caliper and to the end of the
brake chamber push rod. Do not apply an excessive amount of grease.
CAUTION: DO NOT attempt to loosen clamp band bolt in order to rotate and reposition the air
inlet ports. DO NOT use clamping tools such as vise grips to hold the push rod. The spring
brake actuator contains an internal boot to seal the caliper from contaminants and may be
damaged if brake chamber is rotated or if clamping tools are used on the push rod.
CAUTION: Ensure brake chamber is properly positioned so that the breather tube is facing
directly downward toward the road surface.

d.

Carefully install brake chamber on brake caliper assembly.

e.

Install the M16 lock nuts using Never Seez® NF P/N 5928660 and torque to 25 ft-lb (34 Nm) initially and
then to 133 – 155 ft-lb (180 – 210 Nm).

f.

Connect air fittings for the air-lines as marked during removal, to the brake chamber and torque the airline fittings to 25 – 30 ft-lb (34 – 40 Nm).

24. Re-install the ABS sensor wires at either wheel.
25. Re-install the brake drag sensors at either wheel.
26. Remove the upper radius rods from the old axle assembly and install them on the new axle assembly. Apply
Never Seez® NF P/N 5928660 to the bolt threads. Snug the bolts but do not torque.
27. Remove the lower radius rods from the old axle assembly and install them on the new axle assembly. Apply
Never Seez® NF P/N 5928660 to the bolt threads. Snug the bolts but do not torque.
28. Install the tire and wheel assemblies on the axle and torque the bolts to 425 ± 15 ft-lb (576 ± 20 Nm) using a
cross pattern.

Rear Suspension Re-installation.
29. Install the membrane breather bracket NF P/N 393362 on the frame cross member above the curb side upper
radius rod mounting bracket. See Figure 3 for location dimensions.
a.

Using the membrane breather bracket as a template, mark the drilling locations on the frame.

b.

Drill two .166” Dia mounting holes.

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c.

Secure the bracket with two #10 x 5/8” tapping screws NF P/N 34S00010 and two #10 flat washers NF
P/N 10W00000.

Membrane Breather Bracket

Figure 3: Membrane Breather Bracket Mounting Location.
d.

Install the breather removed earlier on the new bracket using two screws 14S04024 and two washers NF
P/N 10W04000.

e.

Install the 90 deg breather elbow NF P/N 392738 on the breather then attach the breather line to the
elbow. Figure 4.

f.

Route the breather line across the chassis cross member towards the street side then rearward above
the upper mount for the forward street side shock absorber. Secure the breather with four p-clamps NF
P/N 092578 and four screws NF P/N 34S00010. Figure 4.
Breather Line

Membrane Breather Bracket

Breather Elbow
Membrane Breather

P-Clips

2
Figure 4: Rear Axle Breather Installation.

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30. Position the suspension cradle and axle under the bus. Using wheel lifts raise the assembly into position.
WARNING:

Make sure the assembly is strapped or chained to the lifting device to prevent it from
tilting or falling.

31. Re-attach the upper radius rods to the chassis using the hardware removed earlier. Using Never Seez® NF
P/N 5928660 on the threads, snug the bolts but do not torque.
32. Re-attach the lower radius rods to the chassis using the hardware remover earlier. Using Never Seez® NF
P/N 5928660 on the threads, snug the bolts but do not torque.
33. Align lower air spring mounting hole with suspension beam mounting pad. Using Never Seez® NF P/N
5928660 on the threads, torque the lock nuts to 20 ft-lb (27 Nm).
34. Install lower end of shock absorbers to suspension cradle with rubber isolators, cupped washers and
locknuts. Using Never Seez® NF P/N 5928660 on the threads, torque the locknuts to 56 ft-lb (76 Nm).
35. Re-connect the air-lines at the rear brake valve mounting plate.
a.

Attach the two previously removed hoses to the quick release valve.

b.

Attach the two previously removed hoses to the relay valve.

36. Re-connect the ABS harness to the vehicle harness.
37. Re-connect the brake wear sensor harness to the vehicle wiring harness.

NOTE:

If the round sensor connector between the wear sensor harness and the extension harness
is unplugged during the removal procedure, check that the rubber seal is not damaged or