1997 GMC Sonoma Owner's Manual - Page 331

I Short TripKity Maintenance Schedule I - 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. v y o u do not use your vehicle under crnp of these conditions, thejluid und.filter do not require changing. Manual transmission fluid doesn't require change. DATE ACTUAL MILEAGE SERVICED B Y 7-21