1999 GMC Sonoma Owner's Manual - Page 328

yellowblue Short Trip/City Scheduled Maintenance 60,000 Miles (100 000 km) (Continued) For Two-Wheel-Drive vehicles only: Clean and repack the front wheel bearings (or at each brake relining, whichever occurs first). 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_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. If you do not use your vehicle under any of these conditions, change the fluid and filter every 50,000 miles (83 000 km). j Inspect engine accessory drive belt. An Emission Control Service. j Replace fuel filter. An Emission Control Service. (See footnote[.) j Replace air cleaner filter. An Emission Control Service. j Inspect fuel tank, cap and lines for damage or leaks. Inspect fuel cap gasket for any damage. Replace parts as needed. An Emission Control Service. (See footnote[.) j Rotate tires. See "Tire Inspection and Rotation" in the Index for proper rotation pattern and additional information. (See footnote +.) j j 7-20