GMC 2006 Sierra 1500 Pickup Owner's Manual page 223

If your vehicle has an Allison transmission, and the fluid
reaches temperatures of approximately 275°F (135°C)
or greater, the driver information center will display a
TRANS HOT IDLE ENGINE warning message and a
chime will sound until the temperature falls below
265°F (129°C). Pull the vehicle off the roadway when
it is safe to do so. Set the parking brake, place the
transmission in PARK (P) and allow the engine to
idle until the transmission temperature falls below
265°F (129°C). If the transmission continues to operate
above 265°F (130°C), contact your nearest dealer or
the GM Roadside Assistance Center. See Roadside
Assistance Program on page 7-6.
Notice: If you drive your vehicle with the
transmission temperature gage above normal
operating range, you can damage the transmission.
This could lead to costly repairs that would not be
covered by your warranty. Do not drive your vehicle
while the transmission temperature gage reading is
above normal. See your dealer for service.
The following situations can cause the transmission to
operate at higher temperatures:
•
Towing a trailer
•
Hot outside air temperatures
•
Vehicle overloading
•
Hauling a large or heavy load
•
Low transmission fluid level
•
High transmission fluid level
•
Restricted air flow to the radiator and the auxiliary
transmission oil cooler (if equipped).
A temporary solution to hotter transmission operating
temperatures may be to let the transmission cool down.
If the transmission is operated at higher temperatures
on a frequent basis, see Scheduled Maintenance
(Gasoline Engine) on page 6-4 for the proper
transmission maintenance intervals.
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