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Transmission Oil temp gauge, sender unit location???

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by JHG, Aug 4, 2002.

  1. JHG

    JHG 1/2 ton status

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    I am starting to put a transmission temperature gauge from B&M in my truck.

    Accourding to the instructions manual I should put the sender unit to the return line from the oil cooler. Probably cause that is the ATF which is going to be used in the tranny.

    But to me it seems more logical to put it in the line from the transmission (but I an not an expert), because that would tell me the heat of the transmission.

    I know they are the experts and are probably right but it doesn´t seem logical. Can somebody explain it to me?

    Jon H.
     
  2. wrathORC

    wrathORC 1/2 ton status

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    Since you probably have rubber lines that need replacing, try each. The only guy I ever knew that ran a gauge on the transmission lines had one on the way in to the cooler and one on the way out with a toggle switch. All the other people I know did the drill-a-hole-in-the-pan type.
     
  3. woody9

    woody9 1/2 ton status

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    Have the B&M gauge myself, and thought that a bit odd to be on the return, but local Tranny shop confirmed the important temp is what's feeding the tranny! Too hot & it's cooked. I went with their recommendation, but think I may add that 2nd sending unit of the 'outbound' side so I can see just how hot things are getting.
    BTW, added a cooler shortly before the gauge, and find it's cooling capabilites excellent! Just returned from a 700 mile trip and tranny only touched 160 twice, for about 3 minutes each time. (warm/warnings i think are in the 200/220+ arena)
     
  4. performance1

    performance1 Registered Member

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    I have an '89 w a 700R4 tranny. Just installed the B&M kit as well, and followed suggestions located elsewhere on this site, which I recommend as well (applicable if you have the 700R4 trans). That is:
    1. On the drivers side of the transmission you will find a "plug" with a hex head, parallel with the ground. If you remove this, the sender unit included with the B&M kit is a PERFECT FIT to replace this plug, same diameter and thread pitch. This makes the installation VERY EASY and eliminates the need to cut cooler lines. Remember teflon tape for the threads to eliminate leaks.
    2. By using this plug location you get a reading on how hot your tranny is, not how cool the return fluid is. Which would you prefer? Personally I'm more interested in knowing how hot my tranny is.
    3. After doing this I was suprised to find out that I really do need to add an external tranny cooler (But then again I live in Southern California where it should have been original equipment with the heat we get here)
     
  5. woody9

    woody9 1/2 ton status

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    What sort of temp readings are you getting? I'd be interested to see what they change to when/if you add the cooler?!!
     
  6. performance1

    performance1 Registered Member

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    Finding that with freeway driving on warm days (80+ outside temps) trans easily gets into "yellow" area (220+) and on occasion touches red (260). You can bet that a tranny cooler is high on my "to-do" list... especially since this is a recently rebuilt trans (9 months ago).
     
  7. h0wl0ngcanitbe

    h0wl0ngcanitbe 1/2 ton status

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    hey can you tell me which one is the spot for the sender, i just got a autometer gauge and im asuming the sender goes in the same place? here is a pic of my tranny.

    [​IMG]

    is it 1,2, or 3?
     
  8. Big Truck

    Big Truck 1/2 ton status

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    1 is where performance1 is taking about where you can get your pressure reading, 2 don't know , 3 you could get the kit to put it in your pan
     
  9. Jason4x4

    Jason4x4 1/2 ton status

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    2 is just part of the casting, that is where the rebuilders put there jig to hold them.
     
  10. h0wl0ngcanitbe

    h0wl0ngcanitbe 1/2 ton status

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    Thanks man i just wanted too be sure!
     
  11. dsmd58

    dsmd58 1/2 ton status

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    i have 700r4 where i installed the sender in the pan. prior to installing the b&m cooler i was getting readings of 200-210 on short drives. now on long drives the trans temp hovers between 160-180. that cooler made a huge difference for me....best mod yet
     
  12. cabledawg

    cabledawg Secret Squirrel Premium Member

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    Number one is a test port for the trans pressure so I'd be weary of putting your temp gauge there. I dont know how much fluid circulation it gets and may not be very accurate. I've been told that the pan is the best location, but trail debris could snag it and cause a huge leak. For offroad vehicles I'd put it on the out side of the cooler lines, becasue you want to now how hot the tranny is, not how well your cooler is working. Just my .02:D
     
  13. h0wl0ngcanitbe

    h0wl0ngcanitbe 1/2 ton status

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    so do i need to drill a hole in the pan or is thier a prebuilt hole i can use to get the best reading?
     
  14. bigblock72

    bigblock72 1/2 ton status Premium Member GMOTM Winner

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    Just use the pressure port hole. It IS accurate and a whole lot easier than putting a fitting in the pan.
     
  15. dyeager535

    dyeager535 1 ton status Premium Member

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    x2. Already hashed out in another thread recently, figures coming off a sender in that location were what everyone else was getting. (apologies if BB72 was that poster lol)

    ONLY concern I'd have is that since it's a pressure test port, leaks are more likely than in the pan, but it's pipe threaded and there's a plug in it already, so not a real big deal.
     
  16. h0wl0ngcanitbe

    h0wl0ngcanitbe 1/2 ton status

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    ya that seems to be the consensus once i get my mounting solution figured out im stickin it their!
     

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