GMC 1996 Sierra Owner's Manual page 269

Automatic Transmission Fluid
When to Check a 1
C' -ge
A good time to check your auromarlc transmission fluid
level is when the engine
oil
is changed.
Change both the fluid and filter every 50,000 miles
(83 000 km) if the vehicle's GVWR is over 8,600 or
if the vehicle is mainly driven under one or more of
these conditions:
In heavy city traffic where the outside temperature
regularly reaches 90°F (32°C) or higher.
0
In hilly or mountainous terrain.
0
When doing frequent trailer towing.
Uses such as found in taxi, police or delivery service.
If your vehicle's GVWR is not over 8,600 and you do
not use your vehicle under any of these conditions, the
fluid and filter do not require changing.
See "Scheduled Maintenance Services'' in the Index.
How to Check
Because this
operation can be a little difficult, you
may choose to have this done
at
your GM 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
i
the fluid could come out and fall on hot engine
~
parts or exhaust system parts, starting a fire. 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).
0
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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