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1991 with 700 R-4 Transmission Cooling Lines to and From Radiator

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by PGL4VT, Aug 13, 2002.

  1. PGL4VT

    PGL4VT Registered Member

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    Which of the two tranmission cooling lines that run to the radiator is the flow return line and vice versa? How can you tell the lines apart without unhooking them and starting the truck?
     
  2. Calclips

    Calclips 1/2 ton status

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    Is this in reguard to installing an aftermarket tranny cooler like in your other post? If it is, I believe that it dosen't matter which way you hook up the lines (somebody correct me if I'm wrong).
     
  3. Scooter

    Scooter 1/2 ton status

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    The top line is the return.
     
  4. mudhog

    mudhog THEGAME Staff Member Super Moderator

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    trace them back from the radiator the top on the radiator is in and the bottom is out so now you know the top line on the radiator is in so follow it back to the tranny and find out what one it is /forums/images/icons/smile.gif
     
  5. PGL4VT

    PGL4VT Registered Member

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    OK fellerz, I did a search and am getting conflicting reports on which line is the true return line from the radiator. BTW, it does matter which line you hook to the new cooler. Per the instructions, you want the return line from the radiator to run to the new cooler. That way, the coolest fluid is being returned to the tranny. Thanks. I'm still confused on which line is the return line.
     
  6. mudhog

    mudhog THEGAME Staff Member Super Moderator

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    take the bottom line from the radiator and go to the top line of new cooler then take the lower new cooler line back to what used to go to the bottom of the radiator. it would go like this in top of radiator out bottom of the radiator in the top of the new cooler out the bottom of the new cooler back to tranny forget the tranny look at the radiator top is in bottom is out
     
  7. Scooter

    Scooter 1/2 ton status

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    had to search back a ways but I knew there were a few links (and more than a few posts) on this topic.

    Leadfoot posted this link back in a post on CK5 in Oct. '01
    http://www.txchange.com/cooler.htm

    Heres a couple I found while searching the 'net:
    http://www.transonline.com/electroPublisher/website/index.cfm?pageID=711
    http://www.technicalevolution.com/coolflw.htm

    FWIW -- I went from the top fitting on the radiator to the bottom of the tranny cooler, then from the top of the tranny cooler back to the top line for the tranny.

    Just my $.02 ..
     
  8. PGL4VT

    PGL4VT Registered Member

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    OK. I know for sure. I just undid both lines and started the truck. The lower line going into the radiator is the pressure line. The upper line is the return. I'm positive as fluid sprayed out ot the lower one. Also, I just installed a drain plug in the tranny pan. $5.19 from NAPA.
     
  9. NewK5Guy

    NewK5Guy 1/2 ton status

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    Hey. Can you tell me which tranny AT THE TRANNY is the return line? I recently hacked both mine off and replaced them with braided line and temp guage but I didn't check to see which line was out and which was in. I would like to move the temp gauge to the tranny out line.
     

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