2007 GMC Sierra 1500 Pickup Owner's Manual - Page 494

Automatic Transmission Fluid (Allison Transmission®) 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 Additional Required Services (Gasoline Engine) on page 621, and be sure to use the transmission fluid listed in Recommended Fluids and Lubricants on page 629. 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. Wait at least 30 minutes before checking the transmission fluid level if you have been driving: • When outside temperatures are above 90°F (32°C). • 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 dealership 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. Checking the Fluid Level Prepare your vehicle as follows: 1. Park your vehicle on a level place. Keep the engine running. 2. With the parking brake applied, place the shift lever in PARK (P). 494