1997 GMC Sonoma Owner's Manual - Page 352

I Long Trip/Highway Maintenance Schedule 37,500 Miles (62 500 km) 0Change engine oil and filter (or every 12 months, whichever occursfirst). An Emission Control Service. 0Check readfront axle fluid level and add fluid as needed. Check constant velocity joints and axle sealsfor leaking. (See footnote **.) 0Rotate tires. See "Tire Inspection and Rotation" in the Index for proper rotation pattern and additional information. (See footnote +.) 0Lubricate chassis components (or every 1'2months, whichever occursfirst). (See footnote #.) DATE ACTUAL MILEAGE SERVICED B Y / -4L