Global Machinery Company Sierra 1999 - Manual (Page 148)

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At approximately 265
_F (130_C), the message center
will display a TRANS FLUID HOT message and the
transmission will enter a transmission protection mode.
When the transmission enters the protection mode, you
may notice a change in the transmission shifting
patterns. The transmission will return to normal shifting
patterns when the transmission fluid temperature falls
below 260
_F (127_C).
See “Message Center” in the Index for
further information.
If the transmission fluid reaches temperatures of
approximately 275
_F (135_C) or greater, the message
center will display a TRANS HOT...IDLE ENG warning
message. 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 260
_F (127_C).
If the transmission continues to operate above 265
_F
(130
_C), please contact your nearest dealer or the
GM Roadside Assistance Center.
NOTICE:
If you keep driving your vehicle with the
transmission temperature gage above the normal
operating range, you can damage the
transmission. This could lead to costly repairs
that may not be covered under your warranty.
The following situations can cause the transmission to
operate at higher temperatures:
D Towing a trailer
D Hot outside air temperatures
D Hauling a large or heavy load
D Low transmission fluid level
D High transmission fluid level
D 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” in the
Index for the proper transmission maintenance intervals.