GMC Sierra 2010 Owner's Manual page 475

2. Flip the handle up, and then pull out the dipstick
and wipe it with a clean rag or paper towel.
3. Install the dipstick by pushing it back in all the way,
wait three seconds, and then pull it back out again.
4. Check both sides of the dipstick and read the lower
level. Repeat the check procedure to verify the
reading.
5. Safe operating level is within the HOT cross hatch
band on the dipstick. If the fluid level is not within
the HOT band, and the transmission temperature
is between 71°C and 93°C (160°F and 200°F), add
or drain fluid as necessary to bring the level into
the HOT band. If the fluid level is low, add only
enough fluid to bring the level into the HOT band.
It does not take much fluid, generally less than
0.5 Liter (1 Pint). Do not overfill.
6. If the fluid level is in the acceptable range, push
the dipstick back in all the way, then flip the handle
down to lock the dipstick in place.
Consistency of Readings
Always check the fluid level at least twice using the
procedure described previously. Consistency
(repeatable readings) is important to maintaining
proper fluid level. If readings are still inconsistent,
contact your dealer/retailer.
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