1995 GMC Yukon Owner's Manual - Page 309

Wait at least 30 minutes before checking the transmission fluid level if you have been driving: 0 When outside temperatures are above 90°F (32°C). At high speed for quite a while. In heavy traffic 0 - especially in hot weather. While pulling a trailer. To get the right reading. the fluid should be at normal operating temperature, which is 180°F to 200°F (82°Cto 93°C). To check transmission fluid hot: Get the vehicle warmed up by driving about 15 miles (24 km) when outside temperatures areabove 50°F (10°C). If it's colder than 50°F (l0"C). drive the vehicle in DRIVE (D) until the engine temperature gage moves and then remains steady for ten minutes. Then follow the hot check procedures. To check transmission fluidcold: A cold check is made after the vehicle has been sitting for eighthours or more with the engine off and is used only as a reference. Let the engine run at idle for five minutes if outside temperatures are 50°F (10°C) ormore. If it's colder than 50°F ( IOOC), you may have to idle the engine longer. Should the tluid level be low during a cold check, you must perform a hot check before adding fluid. This will give you a more accurate reading of the fluid level. To check the fluid hot or cold 0 0 0 Park your vehicle on a level place. Keep the engine running. With the parking brake applied, place the shift lever in PARK (P). With your foot on the brake pedal. move the shift lever through each gear range, pausing for about three seconds in each range. Then, position the shi.ft lever in PARK (P). Let the engine run at idle for three minutes or more. 0 6-27