GMC 2003 Yukon Owner's Manual page 478

97,500 Miles (162 500 km)
Check rear/front axle fluid level and add fluid as
needed. Check constant velocity joints and axle seals
for leaking.
Rotate tires. See Tire Inspection and Rotation on
page 5-62 for proper rotation pattern and additional
information. (See footnote +.)
100,000 Miles (166 000 km)
Inspect spark plug wires. An Emission Control
Service.
Replace spark plugs. An Emission Control Service.
Change automatic transmission fluid and filter if
the vehicle's GVWR is over 8,600 lbs or if the vehicle
is mainly driven under one or more of these
conditions:
− In heavy city traffic where the outside
temperature regularly reaches 90°F (32°C) or
higher.
− In hilly or mountainous terrain.
− When doing frequent trailer towing.
− Uses such as found in taxi, police or delivery
service.
6-10
If you haven't used your vehicle under severe service
conditions listed previously and, therefore, haven't
changed your automatic transmission fluid, change
both the fluid and filter.
Change transfer case fluid.
Except 8.1L V8 Engine: Inspect Positive Crankcase
Ventilation (PCV) valve. An Emission Control
Service.
150,000 Miles (240 000 km)
Drain, flush and refill cooling system (or every
60 months since last service, whichever occurs first).
See Engine Coolant on page 5-26 for what to use.
Inspect hoses. Clean radiator, condenser, pressure
cap and neck. Pressure test the cooling system
and pressure cap. An Emission Control Service.
Inspect engine accessory drive belt. An Emission
Control Service.