Chevrolet 2007 Colorado Owner's Manual page 340

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.
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.
To get the right reading, the fluid should be
at normal operating temperature, which is
180°F to 200°F (82°C to 93°C).
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Get the vehicle warmed up by driving about
15 miles (24 km) when outside temperatures are
above 50°F (10°C). If it is colder than 50°F (10°C),
drive the vehicle in THIRD (3) 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 50°F (10°C), 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.
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).