1996 GMC Sonoma Owner's Manual - Page 330

Long Trip/Highway Maintenance Schedule -- 50,000 Miles (83 000 km) 0Change 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°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 not use your vehicle under m y o f these conditions, tlze,fZuicl and-filter-do not require chnnging. Manual transmission fluid doesn't require change. DATE ACTUAL MILEAGE SERVICED B Y 7-38