There is a big difference in temp readings taken from the pan vs one taken from the line going to the oil cooler. Best place to put the sender is in the line going out of the trans to the cooler. I bought a replacement line from Dodge which had a fitting already built in. My trans temp will normally run 140 to 160 on the highway, but can get up to 250 driving uphill with a load (off road) where your speed can only be around 15 mph. Trans oil temps can get high real fast when the trans cannot get into lockup.
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1996 3500 Clubcab SLT, auto, 4. 10 limited-slip, TST #5, 370s, AFC spring kit, Psycotty, Dunrite converter, Trans-Go, DiPricol EGT, boost & trans temp. gauges, 9 ft. aluminum flatbed and tool boxes with Venco dump. Custom front bumper, Hadley air horn.