Turbo 400 cooling/lines ?

Discussion in 'The "Juice Box"' started by 69_GS_400, Sep 11, 2017.

  1. 69_GS_400

    69_GS_400 Well-Known Member

    Just rebuilt and went through my turbo 400. I also bought a big aluminum radiator. Previously the trans was only cooled by just a trans cooler and the radiator lines were plugged. Now that I bought a new radiator and Freshly rebuilt and put some nice parts in this tranny I want to utilize the radiator plus the trans cooler.
    Right now it looks that my furtherest line to the back (bottom)of the tranny is ran to the top of the cooler and the bottom of the cooler runs right back in to the highest line on the tranny.
    My question is I have new lines. Which I was told should have been 3/8" but those are larger as well as the line bolts. They measured .375 Diaz and the line bolt is .615.
    My old lines are .315 with the line bolt .490. I returned the larger ones because I didn't think they were correct due to new radiator having the same size line bolt as the old. Is this correct?
    Lastly how should my lines run?
    I have a lower tranny line and a higher one. The radiator has 2 inlets one top one bottom and the tranny cooler has a top line and a bottom line as well. I'm not sure which goes where and how to split it when it comes off the radiator to the tranny cooler
  2. BrianTrick

    BrianTrick Brian Trick

    When I ran both,I ran from the lower trans port,to the lower radiator port,then from the upper radiator port,to the cooler,then from the cooler to the upper port in the trans.
    Incase you are thinking of running a remote oil-style filter,do NOT. They do not flow enough volume through them to keep up with the pump. A trans pump flows a lot more than an engine oil pump. Just run the traditional filter inside of the transmission.
  3. Bens99gtp

    Bens99gtp Well-Known Member

    You will want the lower outlet from transfer to go to the lower on rad first then from top of rad to lower on external cooler then from top of cooler back to to of trans.

    By feeding the coolers( both of them ) from the bottom they will push out any air that settles in the system.

    I like to go to the rad first. Almost always water temp will warm up before trans fluid and that will help preheat the trans fluid on cooler driving times. Plus the then you will get the most out of you external cooler as well. As with any oil you don't want it too hot or too cold
    Electra man likes this.
  4. 69_GS_400

    69_GS_400 Well-Known Member

    Thanks much fellas. Do 5/16 lines sound right? That's what I had and I just bought. 3/8 lines seemed to big unless people use an adapter to thread in the line nuts?
  5. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD"

  6. DasRottweiler

    DasRottweiler -BuickAddict-

    Hope this helps.......Jim/Rott
  7. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD"

    The return line is the top line, at the radiator as well as the transmission. The auxiliary cooler goes in line with that line.
  8. mummy68

    mummy68 Silver Level contributor

    Yes It's 5/16 lines. I just installed mine over the weekend so I am sure that is the correct size. I went with the flexible cooler lines. Cost a little bit but they are easier to install especially around the headers. plus they look nice
  9. claude brooks

    claude brooks claude

    just asking,can a cooler be put on my 55 special,my stock cooler is not hooked up.
  10. telriv

    telriv Well-Known Member

    Yes. You DON'T want to run WITHOUT a cooler as it will overheat the fluid & shorten the life of the trans.

    BRUCE ROE Well-Known Member

    Some early cars used the 3/8 lines, later cars all seem to be 5/16. You can change
    by swapping the fitting at the trans, I have some of both in a jar. Bruce Roe

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