1998 GMC Suburban Owner's Manual - Page 312

Refer to the Maintenance Schedule to determine when to replace the air filter. See "Owner Checksand Services" in the Index. Automatic Transmission Fluid If your vehicle has a diesel engine, see "Automatic Transmission Fluid" in the Diesel Supplement. When to Check and Change A good time to check your automatic transmission fluid level is when the engine oil is changed. air cleaner off can Operating the engine with the Change both the fluid and filter every 50,000 miles cause you or others to be burned. The air cleaner (83 000 km) if the vehicle is mainly driven under one or more of these conditions: not only cleans the air, stops flameif the engine it backfires. If it isn't there, and the engine In heavy city traffic where the outside temperature regularly reaches 90°F (32°C) or higher. backfires, you could be burned. Don't drive with it off, and be careful working on the engine with In hilly or mountainous terrain. the air cleaner off. 0 When doing frequent trailer towing. 0 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 100,000 miles (166 000 km). NOTICE: See "Scheduled Maintenance Services" in the Index. If the air cleaner is off, a backfire can cause a How to Check damaging engine fire. And, dirt can easily get Because this operation can be a little difficult, you may into your engine, which damage it. Always will choose to have this done at your GM dealership have the air cleaner in place when you're driving. Service Department. If you do it yourself, be sure to follow all the instructions here, or you could get a false reading on the dipstick. ~ 6-20