GMC 1996 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 temperature gage
moves and then remains steady for 10 minutes. Then
follow the hot check procedures.
Checking Transmission Fluid Cold
A cold check is made after the vehicle has been sitting
for eight hours 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) 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.
Checking the Fluid Hot 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).
0
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).
Let the engine run at idle for three minutes or more.