GMC 1998 Savana Van Owner's Manual page 349

Long TripMighway Maintenance Schedule
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Gasoline Engines
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0
Change automatic transmission fluid and filter if the vehicle's
GVWR
is
over 8600 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
- In hilly or mountainous terrain.
-
When doing frequent trailer towing.
(32°C) or higher.
-
Uses such as found in taxi, police or delivery service.
previously and, therefore, haven't changed your automatic transmission fluid,
change both the fluid and filter.
An Emission Control Service.
0
If you haven't used your vehicle under severe service conditions listed
0
Inspect Positive Crankcase Ventilation (PCV) valve.
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" in the Index 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.
DATE
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7-37