1996 GMC Sonoma Owner's Manual - Page 338

Long Tripmighway daintenance Schedule 100,000 Miles (I 66 000 km) (Continued) c] Change automatic transmission fluid and filter if the vehicle is mainly driven under one or more of these conditions: - In heavy city traffic where the outside temperature regularly reaches 90 O 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. I f you do rzot L L S ~your vehicle m d e r any o f these conditiom, thecfluid d f i l t e r do n.ot m m p i r e changing. Manual transmission fluid doesn't require change. 0Inspect Positive Crankcase Ventilation (PCV) valve. An Emission Colltrol %]-vice. 7-46