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Projects Best Trans cooling question

Discussion in 'Traditional Hot Rods' started by Sweet & Low, Jan 31, 2018.

  1. Sweet & Low
    Joined: Feb 13, 2014
    Posts: 290

    Sweet & Low

    I have a fat fender car with a 302 and C4 w a new aluminum radiator. It has two tranny cooling lines at the bottom tank. I have had two different guy's tell me they would change that to just an in the air tranny cooler by its self for way better trans cooling and plug off the lines at the radiator. What do you guy's think. If so what is the best tranny fluid on the market?
  2. manyolcars
    Joined: Mar 30, 2001
    Posts: 8,536


    cooler in the radiator brings transmission oil up to operating temperature in cold weather
    blowby, porknbeaner and Elcohaulic like this.
  3. woodhawg
    Joined: Apr 11, 2009
    Posts: 1,019

    1. S.F.C.C.

    Mine has a small dedicated trans cooler. Is about 4" hight and 6" wide. Hid it under the frame beside the tranny. Never had any problems hot or cold weather. Car is in my profile. Also 302 with C4. My radiator is custom made and has no tranny cooling in it. Running normal Ford tranny fluid. Works fine.
  4. You can add an auxiliary trans cooler in series with the radiator one, the trans needs to not be too hot or too cold. All of the fleet work trucks that I service are set up that way and they live a much harder life than anything we drive.
    little red 50 likes this.

  5. elba
    Joined: Feb 9, 2013
    Posts: 628


    I have O/H many T-350 transmissions . I put many miles on a 38 Chevy sedan and I didn't run a transmission cooler . Just a line from outlet to inlet . I put a T-400 converter in it which holds about a quart more fluid. Never ever a problem. The early Power glides didn't have a cooler and did fine .
  6. mcsfabrication
    Joined: Nov 26, 2006
    Posts: 974


    External cooler, if the cooler in the radiator has an issue, you end up pumping anti-freeze through your trans. Transmissions and anti-freeze are not a good combination.
  7. Nemosgarage
    Joined: Sep 21, 2009
    Posts: 137


    Stay with the cooler in the radiator and if possible add and additional cooler too. Earlier transmissions did not have this type of cooling which caused premature transmission failure.
  8. Transmission fluid has an operating temperature same as motor oil. Too cold and you get hard shifts, too hot and you burn up clutches. There is a reason that the auto manufactures use the radiator to cool the transmission. That reason has been mentioned above, to obtain correct operating temperature. I see know need for an extra cooler unless you are towing or perhaps have an extreme high output engine or race the car.
  9. mgtstumpy
    Joined: Jul 20, 2006
    Posts: 9,005


    I've always advocated using the OEM radiator and an auxiliary cooler based on advice. The consensus is to run transmission coolers in a series, from pressure outlet of transmission through radiator first and then through an auxiliary cooler before going back to transmission.

    Firstly, the reasons for this is that if the transmission fluid is hot, it will be cooled more quickly and efficiently by the radiator. Secondly, if it is cool it will be warmed up and yes they can run too cool. When they run cool condensation that may be in the system remains there, NOT GOOD. The transmission needs heat for self preservation but not too much.

    If the fluid is too hot after it leaves the radiator it will be cooled by the auxiliary cooler before going back to the transmission. Auxiliary coolers needs to be mounted where airflow isn't impeded as it needs to dissipate or radiate the heat, air flowing through and over does the job. If stuck for space a small slimline auxiliary coolers with a fan as you propose is the go.

    In colder areas and on short trips, the transmission may not get hot enough to reach optimum operating temperature. By being routed through radiator firstly it will be heated to a better temperature.

    I checked my late model in the garage and this is the way the big manufacturers now do it. They spend $M on R&D so why not take advantage of their expertise, it's free. I wouldn't recommend just running an auxiliary cooler, my opinion, but definitely use your radiator. Why, because the transmission generates the second greatest amount of heat beside the engine.

    Another thing, I always use coolant rather than water. It costs a little more but a lot more advantages. Water has contaminants that may lead to blockages and corrosion. Coolant also lubricates your water pump. A good radiator also helps.

    I personally prefer to run fluid line through the radiator first and then back through auxiliary transmission cooler. I've seen small air deflectors used to push air over and/or coolers in some instances where space is an issue. Don't have it too low so that you run the risk off loosing it due to road clearance issues. Last thing you want to do is grenade your transmission due to heat buildup and heat will kill them eventually. I've never been a fan of just a stand alone transmission cooler in isolation.

    As I'm building a stout 383 with a similar 700R and stall convertor in my '46 Olds, I'm also running a deep pan but don't forget to match the pan with the correct pickup that sits down where it should near the base of the pan, a lot of additional fluid to cool.

    Normal transmission range is between 180F- 250F with pan temperature @ 60mph being 180F. Any more that 20mins @300F and you could need some repairs. When towing a load the temp can easily rise to 250F.

    Good fluid is pink, red means used, Brown or with a red tint means too long. heatchrt.jpg
  10. Remember the legendary GM Hydramatic; built from the late 40s thru the early 60s, powered the nation, did not have the super efficient lock-up torque converters of today's creampuffs rather had an always slipping fluid coupling, a not too efficient heat transferring case of cast iron, was originally designed fro military tanks (although those had a cooling coil in the pan of the tranny) and had zero cooling provisions. At least the PowerGlide trannys on low powered cars had vented bell housings and the torque converters had air cooling baffles welded to it. The vast majority of cars don't need much tranny cooling, they need the radiator connection to warm them to operating temps as discussed previously in this thread. A serious cooler is only needed in high output situations; towing, hill climbing, long races.
    On my '53 Chevy pickup running a warm 235 six and 200R4 OD tranny I use an auxiliary 10" radiator with a thermostatically controlled cooling fan and fluid bypass thermostat. The fluid bypasses the radiator most of the time and the fan rarely if ever comes on.
  11. Sweet & Low
    Joined: Feb 13, 2014
    Posts: 290

    Sweet & Low

    Thanks Much for the info guy's. Looks like I'll be shopping for a trans cooler to add to the radiator return line as a combo system.
  12. Where it really becomes a problem cooling wise is in a tow vehicle. I think that factory they use the aux cooler in conjunction with the radiator. I got an idea that the aux cooler is for when you're towing and they use the radiator to regulate it.

    @mcsfabrication mentioned the problem with the salamander in the rad tank. I had one rupture on an off road vehicle when I was in Mexico. Cost me the rad repair and a complete rebuild on the tranny. We didn't hook back up to the rad and went with an external cooler. I think that one that gets jolted and jostled around a lot is probably more prone to breakage than one that we drive on the street.

    There are two schools of thought on the external trans cooler, both have merit and you just need to decide which one will work for you. One is that the transmission brings coolent temps up if you run it through the radiator. The other is that your tranny will remain at a constant temp if you use the radiator. Both consider that yes your transmission needs to be cooled.
  13. LM14
    Joined: Dec 18, 2009
    Posts: 1,937

    Member Emeritus
    from Iowa

    I've been asking this same question and a few others about trans coolers to local shops and on a couple other web groups. Here's what I decided to do.

    Running the cooler in the bottom of my Walker Cobra radiator, period. If it runs hot I can always add another cooler in series pretty easily.

    I ended up using 5/16 hard line except about 9" or Fragola PTFE braided and coated line for a flex section. Still needs some clamps and hangers but I have it roughed in now. Everything is still finger tight right now.


    cooler1.jpg cooler2.png cooler3.png cooler4.png cooler5.png cooler6.png cooler7.png
  14. 28 Ford PU
    Joined: Jan 9, 2015
    Posts: 457

    28 Ford PU
    from Upstate NY

    I'm running a 28 ford PU with fenders. I mounted one of those small trans coolers up under the splash apron where you have tons of air flow.

    Sent from my iPad using H.A.M.B.

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