2004 GMC Sierra 1500 Pickup Owner's Manual - Page 211

It also provides an indicator of how hard your vehicle is working. During a majority of the operation, the gage will read 210°F (100°C) or less. If you are pulling a load or going up hills, it is normal for the temperature to fluctuate and approach the 250°F (122°C) mark. If the gage reaches the 260°F (125°C) mark, it indicates that the cooling system is working beyond its capacity. See Engine Overheating on page 5-36. When your ignition is on, the gage shows the temperature of the transmission fluid. The normal operating range is from 100°F (38°C) to about 265°F (130°C). At approximately 265°F (130°C), the driver information center will display a TRANSMISSION 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 Driver Information Center (DIC) on page 3-55 for further information. Transmission Temperature Gage United States Canada Your vehicle may be equipped with a transmission temperature gage. 3-47