Originally Posted by jbenoit28
What is too hot for the transmission on the Tahoe?
The tranny engineers and developers say 225° F. sump temp is the redline for any ATF in any automagic tranny. You can exceed 225° F. only if you can see the top of the pass in front of you. Otherwise, stop, put the tranny in neutral or park, elevate the idle RPM to 1,300, and twiddle your thumbs until the tranny temp drops to below 210°.
With my previous tow vehicle, I added an analog tranny temp gauge that gave me sump temp. I had an aftermarket oil-to-air tranny cooler that was much, much bigger than stock, and I never saw over 205°. I also used Mobil 1 synthetic ATF and changed it every 30k miles. I had zero tranny problems during almost 200,000 miles including about 100,000 miles of towing an 8,000 pound 5er.
My 2012 F-150 Lariat has a built-in digital tranny temp gauge. It runs a bit warmer than my old F-250 diesel, but never even close to 225° F. Usually around 192° and rarely up to 205°.
2002-up Ford SuperDuty pickups had a factory tranny temp gauge, but it was misleading. Green meant go. Yellow meant you were too hot, so stop and cool off. Red meant bend over and kiss your ole hiney goodby, because your tranny is cooked. Much better than the factory gauge was to add an aftermarket gauge with numbers from 100° to 280°, so you knew for sure when you were getting close to 225°. Most tranny temp gauges go from 140° to 320°,but with those you never see the gauge move off the peg in the wintertime, so you wonder if it still works. Most automagic trannies will get over 100°, even in 40-below weather, so 100° is a good number for the bottom peg.