1998 Chevrolet Express Van Owner's Manual - Page 257

Uses such as found in taxi, police or delivery service. If your vehicle's GVWR is not over 8,600 and you do not use your vehicle under of these conditions, any change the fluid and filter every 100,000 miles (166 000 km). See "Scheduled Maintenance Services"in the Index. Wait at least30 minutes before checking the transmission fluid level if you have been driving: 0 0 When outside temperatures are above 90°F (32°C). At high speed for quite a while. In heavy traffic -- especially in hot weather. 0 How to Check Because this operationcan be a little difficult, you may choose to have thisdone at your GM dealership Service Department. If you do it yourself, besure to follow all the instructions here, or you could get a false reading on the dipstick. While pulling a trailer. To get the right reading, thefluid should be at normal operating temperature, which is 180°F to 200°F (82°C to93"C). See "Checking Transmission Fluid Hot" in the Index. Checking Transmission Fluid Hot Get the vehicle warmed up by driving about15 miles (24 km) whenoutside temperatures are above50°F (10°C). If it's colder than 50°F (lO"C), drive the vehicle in in DRIVE (D) until the engine temperature gage moves and then remains steady for 10 minutes. Then follow the hot check procedures. NOTICE: Too much or too little fluid can damage your transmission. Too much can mean that some of the fluid could come out and fall on hot engine Be parts or exhaust system parts, starting a fire. sure to get an accurate reading if you check your transmission fluid.