GMC 2002 Sierra - Manual (Page 390)

6-23
How to Check
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.
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:
D When outside temperatures are above 90_F (32_C).
D At high speed for quite a while.
D In heavy traffic
-- especially in hot weather.
D 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).
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 (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’s 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.