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Technical Transmission fluid cooling lines w/cross flow radiator

Discussion in 'The Hokey Ass Message Board' started by Jeff Osstyn, Aug 16, 2020.

  1. Jeff Osstyn
    Joined: Mar 21, 2016
    Posts: 21

    Jeff Osstyn
    Member

    Crossflow radiator, drivers side top inlet from hot thermostat. Bottom outlet passenger side to water pump cooled water. OEM routes transmission fluid lines first to the bottom passenger side of the in radiator trans fluid cooler. So hot trans fluid goes to the cooler side of the radiator first, which would actually heat the water going to the pump and cool the trans fluid. Now as the trans fluid flows upward to the exit of the cooler it encounters hotter water, re-heating the trans fluid before exiting back to the trans? Seems to me that this would cause higher transmission fluid temps.
    So what is the reason for routing the lines this way? Seems to me you would be sending fluid back to the transmission at the temp the thermostat is, 180 degrees or so? Why not switch the trans lines to the cooler? Sending fluid back at the temp of the exit from the radiator to the water pump. Something less than 180 deg.
     
  2. ...I'd suggest using a cooler along side the trans mounted on the frame where it will get good airflow.,...have used these for years with no problems,...keeps the heat from the radiator separate from the trans.
    ...you can use short solid lines as long as you use a short length of rubber line to allow for any movement.
     
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  3. Hnstray
    Joined: Aug 23, 2009
    Posts: 11,585

    Hnstray
    ALLIANCE MEMBER
    from Quincy, IL

    @Jeff Osstyn

    I am having difficulty following your description. You refer to the radiator as ‘cross flow’, which in my mind means radiator tubes are horizontal and the tanks are vertical, on the sides. If that is the case, and the trans cooler lines are both attached to same tank, the one that returns water to the pump, then the trans cooler IS in the cooler water flow. If that is the case, I don’t see the problem. What am I missing here?

    Ray
     
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  4. squirrel
    Joined: Sep 23, 2004
    Posts: 46,872

    squirrel
    Member

    The tank with the cooler in it is the "cold" side of the radiator...it doesn't matter which line is top or bottom.

    Just another way to say what Ray said.
     
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  5. Kevin Ardinger
    Joined: Aug 31, 2019
    Posts: 231

    Kevin Ardinger

    The radiator does actually warm the trans fluid as well for colder weather. It will usually run about the same as engine coolant temp. If you want it cooler, as I would, just add an external cooler or bypass the radiator all together and run a big external cooler.


    Sent from my iPad using The H.A.M.B. mobile app
     
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  6. 2OLD2FAST
    Joined: Feb 3, 2010
    Posts: 2,736

    2OLD2FAST
    Member
    from illinois

    ATF needs to be 175-200° , cooler than that can cause trans damage , dome new trans won't upshift until the trans warms to a preset temp !
     
    Elcohaulic likes this.
  7. George
    Joined: Jan 1, 2005
    Posts: 7,286

    George
    Member

    routed mine to the top, after leaving goes to a remote filter.
     
  8. Jeff Osstyn
    Joined: Mar 21, 2016
    Posts: 21

    Jeff Osstyn
    Member

    Not according to the OEM's.
     
  9. Jeff Osstyn
    Joined: Mar 21, 2016
    Posts: 21

    Jeff Osstyn
    Member

    I have been running my lines opposite from the OEM's and transmission guys recommendations for years. Not sure if it makes the trans temps any different? But to me it seems the trans would run cooler, possibly makes the engine water warmer? I am going to install a temp gauge and compare the different temps with different routings of lines and see what I come up with.
     
  10. Jeff Osstyn
    Joined: Mar 21, 2016
    Posts: 21

    Jeff Osstyn
    Member

    Radiator with side tanks, crossflow. Drivers side top inlet from thermostat. Passenger side bottom outlet, cold water to pump. So, hot water top drivers side, cold bottom passenger side. Trans cooler in the passenger side tank, so to me the top of the trans cooler is hot, the bottom is colder. The OEM's route the trans fluid in at the cold side and out the hot side of the trans cooler in the radiator.
     
  11. Mr48chev
    Joined: Dec 28, 2007
    Posts: 27,533

    Mr48chev
    ALLIANCE MEMBER

    On OEM radiators the coolant doesn't zig zag down though the radiator as many imagine. It drops down in the inlet side, crosses across to the outlet tank and out the hose to the water pump. There is no frigging difference in temp top to bottom on the outlet side as it is one pass across and done. that is a fallacy or figment of imagination.

    There might be an aftermarket radiator that is sectioned off in the tanks to direct coolant in a zig zag pattern but I don't remember seeing adds for one.
     
    Last edited: Aug 16, 2020
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  12. 2OLD2FAST
    Joined: Feb 3, 2010
    Posts: 2,736

    2OLD2FAST
    Member
    from illinois

    Finally ! Thank you !
     
  13. Hnstray
    Joined: Aug 23, 2009
    Posts: 11,585

    Hnstray
    ALLIANCE MEMBER
    from Quincy, IL

    I believe you have a misconception of the process. @Mr48chev and @squirrel explain it above, as long as the cooler is located in the tank that is after the water has passed through the core, it is the cool side. Any minor variations in coolant temperature through any of the core tubes are quickly blended into a single temperature in the tank. For all practical purposes, it matters not which end of the trans cooler element in that tank that the hot trans fluid enters and which it exits. It sheds the same amount of heat whichever direction it flows.

    Ray
     
    Last edited: Aug 16, 2020
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  14. sdluck
    Joined: Sep 19, 2006
    Posts: 2,527

    sdluck
    Member

    The cooler lines are also to use rad coolant to help warm the trans
     
  15. squirrel
    Joined: Sep 23, 2004
    Posts: 46,872

    squirrel
    Member

    Get out your infrared temp gun and see how hot the tanks are, in various places.

    Sent from my Trimline
     
  16. 2 times I had a cross flow radiator trans cooler fail. The spiral internal metal line broke inside the side tank allowing trans fluid to get into the water and water into the trans. I will never use a radiator for cooling a trans again. Just use an external cooler for your trans.
     
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  17. Jeff Osstyn
    Joined: Mar 21, 2016
    Posts: 21

    Jeff Osstyn
    Member

    Thanks for the responses!
     
  18. Jeff Osstyn
    Joined: Mar 21, 2016
    Posts: 21

    Jeff Osstyn
    Member

    Yes, Eastwood sells a radiator that is sectioned off, makes 3 sections in a cross flow radiator. I have one on another vehicle, but it has a manual trans so no internal trans cooler. I guess my question came up due to everything written about how to route lines is always the same, 'output from trans goes to bottom of trans cooler'. The OEM' and aftermarket all print the same thing. I was wondering why? Made no sense.
     
  19. Jeff Osstyn
    Joined: Mar 21, 2016
    Posts: 21

    Jeff Osstyn
    Member

    So this temp would be at the output of the trans? If yes, the input temps would need to be much lower. 50 degrees lower? I am getting the feeling that to get this low of a input temp consistently you would need a completely separate trans cooling system, with it's own fan and temp control. As others have mentioned.
     
  20. Jeff Osstyn
    Joined: Mar 21, 2016
    Posts: 21

    Jeff Osstyn
    Member

    Thanks!
     

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