Just installed an Autometer tranny temp gauge myself. Sensor "tee'd" into transmission cooler outlet line back to the transmission. Runs about 185-210 degrees F, but got north of 250 degrees F ( pegs gauge) droning interstate @ 105F OAT (outside air temperature) on current trip out of Phoenix to Big Bear Lake, CA. Transmission fluid just changed when I installed the sensor.  When checking tranny fluid after droning on I-10 it was correct level and red. I do  need to check outlet temp from cooler with infrared gun when I get home from current trip. 

I have a '89 Westy automatic with 2.2L Subie conversion.

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