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trans temp gauge help

Discussion in 'Truck & Equipment Repair' started by Detroitdan, Dec 18, 2005.

  1. Detroitdan

    Detroitdan PlowSite.com Addict
    Messages: 1,937

    I need to put a trans temp gauge in, rather than spend $55 or more for a new one, I thought I would use one I already have. It is an oil temp gauge, but I think the temp range is the same, actually goes up a little higher, but I think it should work. I have the brass fitting and sender to put in the line, the only problem is at some point years ago I took it out of the box and lost the directions. Anybody got any idea how to wire it up? On the back of the new gauge there is one black wire that goes to the light. Then there are four brass threaded posts, one marked G (must be ground), one is marked S (maybe sender?) one is marked I (no idea) and one is not marked. I think the unmarked one may be left empty, because it doesn't have a double nut to attach a wire with. I think that if "G" is ground, and "S" is sender then "I" must be power, right? Just wanted to try to make sure before I hook it up wrong and short it out or something. Any help would be appreciated.

    Oh, one more thing, I want to put it on the line coming out of the cooler, is there a quick way to tell which is which?
  2. brunosplace

    brunosplace Senior Member
    Messages: 282

    put the gauge on the line before the cooler, so that you know the actual temp of the trans, not just the cooled oil. as for telling which is the feed from the trans, start the truck & and run it a couple of minutes, then feel the lines, the hotter one is from the trans. Best to check it back by the trans, where it'll be more noticable. On the gauge wiring you may be able to check the manufacturers website.
  3. KeeblerBP

    KeeblerBP Member
    Messages: 35

    I think you are right with what everything stands for on the back of the gauge. The "I" probably stands for Ignition so it is not draining your battery when the truck is off.
  4. Detroitdan

    Detroitdan PlowSite.com Addict
    Messages: 1,937

    thanks for the input, keebler, I never even thought of ignition. I tried to think of any other word that would translate to power source, but I couldn't come up with anything.
    Bruno, I knew somebody would suggest running it to check, I was hoping to find an easier way. My trans cooling system is apparently big enough that it doesn't heat the lines up noticeably, I don't think I could tell unless I hooked up my trailer and pulled it up a mountain. In fact, a couple months ago I had a driveline noise I couldn't identify, and while looking around for it I noticed both lines at transmission were quite cool after driving it. I immediately thought there was a blockage somewhere and the fluid wasn't circulating, so I went to a superb local transmission shop. They unhooked a line and pressure checked the system anyway, and it was fine, but they told me it won't heat up enough to feel by touch, unless you are really working it hard, because my system is so big and holds a lot of fluid. I couldn't believe it, but this guy is a real pro and a class act, after 30 years rebuilding trannies I gotta figure he knows something. I thought the same as you about the trans temp sender location, but I asked him about that too, and he surprised me again by saying that the output of the trans matters not at all, you need to know the temp of the fluid that you are feeding it to know if the cooler is keeping up. He said the fluid coming out is always going to read hot, but as long as it gets cool fluid circulated back into it you won't hurt anything. So I guess you would be more likely to be nervous about the temps you are reading, whereas with it after the cooler you will really know when it gets too hot for the cooler to keep up, which is when I switch on the fan.
    Thanks for the responses, I appreciate it.
  5. andcon83

    andcon83 Senior Member
    Messages: 388

    If you have the means, you maybe would want to think about putting it in the transmission pan itself. This would give you a more accurate reading of what the temp. was. Unless it is made for in line use. Just a thought.