GMC 2005 T-Series Owner's Manual page 247

36,000 Miles (55 000 km)
Vehicles Without Engine Oil Life System Only:
Change engine oil and filter (or every 12 months, or
every 600 hours of engine operation, whichever
occurs first). (2)
Vehicles With Engine Oil Life System Only: Check oil
life system (or every 600 hours of engine operation,
whichever occurs first). If engine oil and filter are
changed, reset system. See Engine Oil Life System
on page 5-18. (2) (8)
37,500 Miles (60 000 km)
Check fluid levels (or every 3 months, whichever
occurs first). (1) (5)
Chassis lubrication service (or every 6 months,
whichever occurs first). (10)
Wheels and tires service. (13)
Hydraulic brake service (or every 6 months,
whichever occurs first). (6) (30)
Parking brake service (or every 6 months, whichever
occurs first). (7)
Air brake service (or every 6 months, whichever
occurs first). (26)
Air brake automatic slack adjuster service (or every
500 hours, whichever occurs first). (27)
Check air brake relay valve operation and check for
leaks (or every month, or every 300 hours, whichever
occurs first).
Clean air brake application valve (or every 3 months,
or every 300 hours, whichever occurs first). Lubricate
linkage.
Air brake chamber service (or every 2 months,
whichever occurs first). (28)
6-9