GMC 2003 GMT560 T-Series Owner's Manual page 250

Shields and underhood insulation service. (4) (5) (21)
Rear axle air shift motor service. (11)
Air intake system service (or every 24 months,
whichever occurs first). (4) (5) (24)
97,500 Miles (156 000 km)
Check fluid levels (or every 3 months, whichever
occurs first). (1) (6)
Chassis lubrication service (or every 6 months,
whichever occurs first). (12)
Wheels and tires service. (15)
100,000 Miles (160 000 km)
Change engine oil and filter (or every 12 months,
whichever occurs first). (2) (3)
Inspect engine drive belt; replace as necessary.
Change power steering fluid (or every 36 months,
whichever occurs first). (13)
Replace power steering reservoir filter element (or
every 24 months, whichever occurs first).
Front axle service. (38)
Rear axle service – Eaton, Rockwell, Spicer Axles
(or every 12 months, whichever occurs first). (37)
Exhaust brake service (if equipped). Check for
excessive spindle free play and smooth operation.
Lubricate ball joint cap.
6-16
Air compressor dry element pleated paper air strainer
service (or every 2 months or every 800 hours,
whichever occurs first).
Inspect air compressor discharge port (or every
6 months or every 1,800 hours, whichever occurs
first).
Manual transmission (ZF 6–speed only) fluid
replacement (or every 48 months, whichever
occurs first).
150,000 Miles (240 000 km)
Cooling system service (or every 60 months since
last service, whichever occurs first). (3) (35)
Inspect engine drive belt; replace as necessary.
200,000 Miles (320 000 km)
Remove, disassemble, clean and inspect the air
brake trailer supply valve (or every 2 years, or
every 7,200 hours, whichever occurs first).
Inspect engine drive belt; replace as necessary.
250,000 Miles (400 000 km)
Rear axle service – Eaton, Rockwell, Spicer Axles
(or every 36 months, whichever occurs first). (37)