TM-9-2320-272-24-4
TRUCK, 5-TON, 6X6, M939, M939A1, AND M939A2 SERIES TRUCKS (DIESEL)
TECHNICAL MANUAL; UNIT, DIRECT SUPPORT, AND GENERAL SUPPORT MAINTENANCE MANUAL; VOLUME 4 OF 4
JUNE 1998
TM-9-2320-272-24-4 - Page 64 of 836
TM 9-2320-272-24-4
5-9. CAMSHAFT AND GEAR MAINTENANCE
THIS TASK COVERS:
a.
Check Backlash
b.
Removal
c.
Disassembly
d.
Cleaning and Inspection
e.
Assembly
f.
Installation
INITIAL SETUP:
APPLICABLE MODELS
M939/A1
SPECIAL TOOLS
Telescoping gauge (Appendix E, Item 136)
Cam bushing replacement tool (Appendix E,
Item 26)
TOOLS
General mechanic’s tool kit (Appendix E, Item 1)
Dial indicator (Appendix E, Item 36)
Puller kit (Appendix E, Item 102)
Outside micrometer (Appendix E, Item 80)
Vernier caliper (Appendix E, Item 159)
Brass rod
a. Check Backlash
MATERIALS/PARTS
Seven cam bushings (Appendix D, Item 34)
Camshaft bushing (Appendix D, item 33)
Lubricating oil (Appendix C, Item 50)
Drycleaning solvent (Appendix C, Item 71)
REFERENCES (TM)
TM 9-2320-272-24P
EQUIPMENT CONDITION
l
Engine oil pan removed (para. 4-22).
l
Piston and connecting rod installed (para. 5-10).
GENERAL SAFETY INSTRUCTIONS
l
Keep tire extinguisher nearby when using
drycleaning solvent.
l
Drycleaning solvent is flammable and toxic. Do
not use near an open flame.
1.
Attach dial indicator to engine block (3) and rotate camshaft gear (2) as far as it will freely move
and hold it in place. Ensure crankshaft gear (1) does not move.
2.
Position dial indicator arm to camshaft gear (2) tooth and set dial indicator to zero.
3.
Rotate camshaft gear (2) in opposite direction and read backlash measurement as rotation stops. If
backlash is not 0.002-0.020 in. (0.05-0.51 mm), replace camshaft gear (2).
NOTE
Normal backlash is 0.0045-0.0105 in. (0.114-0.267 mm) on new
gear with a minimum of 0.002 in. (0.05 mm).
b. Removal
Rotate camshaft gear (2) and camshaft (4) slightly and remove from engine block (3).
CAUTION
Use care when removing camshaft to avoid damaging bearings.
5-58
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