GMC 2003 C4C042 Owner's Manual page 353

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Wheel bearing (grease type) service (or every
24 months, whichever occurs first, and whenever
hubs are removed). (23)(46)
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Wheels and tires service. (15)
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Parking brake service (or every 6 months, whichever
occurs first). (8)
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Air intake system service (or every 24 months,
whichever occurs first). (4)(5)(24)
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Evaporative Control System service (if equipped) (or
every 24 months, whichever occurs first). (3)(26)
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Rear axle air shift motor service. (11)
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Air brake service (or every 6 months, whichever
occurs first). (39)
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Air brake automatic slack adjuster service
(or every 500 hours, whichever occurs first). (40)
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Check air brake relay valve operation and check
for leaks (or every month, or every 300 hours,
whichever occurs first).
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Clean air brake application valve (or every 3 months,
or every 300 hours, whichever occurs first); lubricate
linkage.
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Air brake chamber service (or every 2 months,
whichever occurs first). (41)
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Trailer brake hand control valve service (or every
3 months, or every 900 hours, whichever
occurs first). (42)
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L18/LB7 Engines Only: Clutch pedal free
travel service. (10)
30,000 Miles (48 000 km)
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Gasoline Engine Only: Check Oil Life System.
If engine oil and filter are changed, reset system.
See "Engine Oil" in the Index. (3)(9)
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DURAMAX
and filter (or every 12 months, whichever occurs
first). (2)(3)
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Check fluid levels (or every 3 months, whichever
occurs first). (1)(6)
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DURAMAX
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Chassis lubrication service (or every 6 months,
whichever occurs first). (12)
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Replace fuel filter(s) (or every 12 months, whichever
occurs first). (3)
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Steering system service. (13)
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Front and rear suspension service. (14)
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Spring to axle U
service. (16)
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Exhaust system service (or every 6 months,
whichever occurs first). (3)(4)(17)
Diesel Only: Change engine oil
Diesel Only: Replace fuel filter.
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bolts and shackle bolts
(Continued)
7-7