2010 GMC Savana 2500 Cargo Owner's Manual - Page 283

When to Check and Change Automatic Transmission Fluid A good time to check your automatic transmission fluid level is when the engine oil is changed. Change the fluid and filter at the intervals listed in Scheduled Maintenance on page 7-3, and be sure to use the transmission fluid listed in Recommended Fluids and Lubricants on page 7-11. Wait at least 30 minutes before checking the transmission fluid level if you have been driving: When outside temperatures are above 32°C (90°F). At high speed for quite a while. In heavy traffic - especially in hot weather. While pulling a trailer. How to Check Automatic Transmission Fluid Because this operation can be a little difficult, you may choose to have this done at the dealer/retailer 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. 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 parts or exhaust system parts, starting a fire. Too little fluid could cause the transmission to overheat. Be sure to get an accurate reading if you check your transmission fluid. To get the right reading, the fluid should be at normal operating temperature, which is 82°C to 93°C (180°F to 200°F). Get the vehicle warmed up by driving about 24 km (15 miles) when outside temperatures are above 10°C (50°F). If it is colder than 10°C (50°F), drive the vehicle in D (DRIVE) until the engine temperature gage moves and then remains steady for 10 minutes. A cold fluid check can be made after the vehicle has been sitting for eight hours or more with the engine off, but this is used only as a reference. Let the engine run at idle for five minutes if outside temperatures are 50°F (10°C) or more. If it is colder than 10°C (50°F), you may have to idle the engine longer. Should the fluid level be low during this cold check, you must check the fluid hot before adding fluid. Checking the fluid hot will give you a more accurate reading of the fluid level. 6-21