Now i need some ideas from you guys on where to install sensor for trans temp gauge.
The pan, period. Not in a cooler line, not the test port. The pan. Test ports don't get enough flow for accurate readings, especially if the conditions are changing quickly, like when you drive hard. An outgoing transmission line will have fluid at temps that'll make you cry due to being heated in the torque converter. Think 400+°... It's the hottest operating part of a transmission. You can put a sensor here to see how hot it gets, but that's not how hot the actual transmission is, nor is it the temp of the fluid feeding it. Some say it's like having an engine temp sensor in the cylinder heads- the hottest area of the engine- but it's not the same in my opinion.
A sensor on the return line tells you the temp "post cooler" but teeing into that won't get the most accurate, useful info either. The fluid will continue to cool once it enters the pan and joins all the other fluid that's touching surfaces, dissipating the heat. The information you need is at that location: in the transmission pan. Hopefully it's an extra deep, finned pan that drastically helps keep the temps down.
Sensor bung: you can drill a hole and weld a nut on for cheap, or there are bolt together kits that utilize an anaerobic sealer (dries in absence of air). There are weld-in bung kits as well. I don't know if you have a cast aluminum pan but they're so thick that some people have simply tapped them and threaded the sensor in- don't do that. There's not enough meat there for a solid, long lasting connection.
The short version is this: The outgoing transmission fluid temp is not anywhere near an accurate representation of transmission temperature or slippage, and you'll never know if you reach temps high enough to scorch it. You'll ONLY know how hot your converter gets. The cooled fluid line doesn't tell you the temp of the trans but you'll know if the fluid is getting cool enough. Kind of. A sensor in the pan tells you the temp of the fluid you're using and will alert you if your clutches are slipping and heating it up. It also tells you if you've cooled it enough to use. Knowing that information means the converter is happy unless there's a completely different issue.
