1996 GMC Sonoma Owner's Manual - Page 239

Checking Transmission Fluid Hot Get the vehicle warmed up by driving about 15 miles (24 km) when outside temperatures are above 50°F (10°C). If it's colder than 50°F (lO"C), drive the vehicle in DRIVE (Dj until the engine temperaturegage moves and then remains steady for 10 minutes. Then follow the hot check procedures. Checking the FluidHot or Cold Park your vehicle on a level place. Keep the engine running. 0 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 shift lever in PARK (P). 0 Checking Transmission Fluid Cold 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 temperaturesare 50°F (10°C) or more. If it's colder than 50°F (lO°C), you may have to idle the engine longer. Should the fluid level be low during a cold check, you rmst perform a hot check before adding fluid. This will give you a more accurate reading of the fluid level. Let the engine run at idle for three minutes or more.