External transmission oil coolers
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  1. #1
    1000+ Posts Beano's Avatar
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    Default External transmission oil coolers

    Hi gents,
    I own two Peugeots, but am currently helping a mate with his V6 Commodore. It's a 3.8 litre 2004 VY model, low Ks and very original.

    He wants to fit an external auto transmission cooler as Commodores are known for eventually leaking water into the trans from the standard setup, thereby stuffing it up.

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    I agree that it's a good idea (I have a 505 with an external cooler), I don't want to help him fit something which may ultimately damage the car. There seems to be uncertainty about whether an external cooler might make the trans oil TOO cool, which of course is not good.

    >>>> Do people ever fit them with some sort of thermostat which restricts flow like coolant thermostats ?

    >> I've seen some advertised with fans. Do they have a temperature-activated switch ? Perhaps these are only for towing (he is not going to).

    >>>> Also, would it be wise to also fit an inline trans oil filter while we're at it ? Or just rely on the fine gauze in the pickup ? He wants the car to last him a fair few years, and a filter would, in my opinion, remove those tiny particles that will eventually end the life of the transmission prematurely.

    All input appreciated.
    Last edited by Beano; 11th March 2018 at 07:42 PM.

  2. #2
    1000+ Posts PeterT's Avatar
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    It can never be too cool. Visit an auto transmission repairer if in doubt.

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  3. #3
    1000+ Posts Haakon's Avatar
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    You can get trans coolers with their own fan and thermoswitch.
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  4. #4
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    Used to fit them to the R19. Made it run @ <100 deg C. which is desirable. Don't think too cool is a problem in Australia but possibly in Thredbo or Falls in winter?
    No fan needed because i fit the cooler in front of the radiator.
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  5. #5
    1000+ Posts alan moore's Avatar
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    PWR makes trans cooler kits for most Commodores. I had one on my BA Falcon, and was happy with its fit. See Page 31 of the Catalog.
    https://www.pwr.com.au/wp-content/up...logue-2017.pdf
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  6. #6
    1000+ Posts Beano's Avatar
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    Thanks for your input, gents.

    Good point about colder climates....transmissions do have an ideal operating temperature and I'm not sure how much wear they get when going outside this temperature for a long time.

    I may have a quick chat with a transmission place. As they rebuild the things, they would know the outcome of having one.

    I really don't think that cooling the trans oil through the radiator is a good idea. It was probably thought up by the same idiots who decided that transmissions should be sealed for life.......life of that transmission being about 150,000 Ks

  7. #7
    COL
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    The transmission cooler also works as a heater when the transmission fluid is cold, like everything needs to be designed properly to work.
    Regards Col

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  8. #8
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    Default coolers ?

    Quote Originally Posted by Beano View Post
    Thanks for your input, gents.

    Good point about colder climates....transmissions do have an ideal operating temperature and I'm not sure how much wear they get when going outside this temperature for a long time.

    I may have a quick chat with a transmission place. As they rebuild the things, they would know the outcome of having one.

    I really don't think that cooling the trans oil through the radiator is a good idea. It was probably thought up by the same idiots who decided that transmissions should be sealed for life.......life of that transmission being about 150,000 Ks
    Hi Beano
    Transmission coolers have been using the radiator for longer than I have been around so it is no newfangled idea. Not like the sealed transmissions ! However there has been a push for better fuel economy in recent years so bringing the transmission oil up to temperature quickly with the engine temperature helps there. Do not forget that. Normally the temperature of both runs at the thermostat opening temperature for most of the time.

    All newer transmissions have torque converter lockup which means that there is much less churning of the oil and much less heat needing to be disposed of. The computer controller actively monitors the temperature and controls flow in the cooler circuit to control temperature.

    Seems to me that fitting an external cooler may only be of advantage in circumstances where you are towing and/or live in a very hot area. Oil changes would be a better bet probably IMHO for normal commuting work.
    Jaahn

  9. #9
    1000+ Posts Beano's Avatar
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    Food for thought there.....thanks Jaahn.

    Quote Originally Posted by jaahn View Post
    The computer controller actively monitors the temperature and controls flow in the cooler circuit to control temperature.
    But I wonder if a 2004 Commodore would do this ??? I should call a Holden service centre, or ask a transmission place.

    All the same, I have read that the ideal transmission temperature wonder is about 80 degrees, whereas engine temp is about 90. Which could be an argument for an external cooler being put in series with the existing setup. What do you think ?

  10. #10
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    Sophisticated newer car probably have computer controlled oil temps?
    The old R19 had computers but no control. I checked the trans oil temp with and without external oil cooler. With the standard set up it was consistently @ radiator temperature. With a radiator pressure of 15 or more psi the boiling point is quite high and so is the oil temp.
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  11. #11
    1000+ Posts driven's Avatar
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    Best Commodore option is to change fluid every 2 years.
    Above 80 deg C fluid starts to break down.
    Sealed for life is OK if temperature is kept below this 80Deg C
    As good as many General Information - The Transmission Centre

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    Quote Originally Posted by driven View Post
    Best Commodore option is to change fluid every 2 years.
    Above 80 deg C fluid starts to break down.
    Sealed for life is OK if temperature is kept below this 80Deg C
    As good as many General Information - The Transmission Centre
    Hi driven
    That URL is as good as any, yes ! But you misquoted a bit. 80deg is not a magic temperature, any temperature above 0 degrades it.. This is what they said "At 90 degrees C., for instance, fluid life is reduced to 80,000 km. At 110 degrees, which is commonly encountered in many transmissions, the fluid is only good for about 60 000km. At 120 degrees C., the fluid won't go much over 15,000 km. Add another 20 degrees, and life expectancy drops to 8000kms. Go to 150 degrees C., and 1,000 to 1,500 klm is about all you'll get before the transmission burns up."

    However what they fail to say is mostly cruising around the burbs and the freeway at normal speeds the engine temp sits on 85-90+ and the temp of the newer lockup transmissions sits about the same. In winter probably less. So not much drama in normal use. The old trannies with the torque converter churning all the time have gone years ago.

    So just change the oil instead. As the article also says too !! If you are doing more demanding work then it might be worth it to fit something more. The OP mentioned the water leaking into the transmission oil. The cure for that is to change the coolant also. Most likely in a commodore it never gets changed, ever, till something gives up !!! It 'wears out' too ! Might save a few other problems as well.
    Jaahn
    Last edited by jaahn; 13th March 2018 at 05:15 PM.

  13. #13
    1000+ Posts alan moore's Avatar
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    The original fault on the Commodore and some Falcons is the failure of the transmission heat exchanger in the radiator tank that then allows transmission fluid into the cooling system whilst the car is driving, and then has the coolant flow into the transmission on cool down as the radiator is still under pressure. You then go and start up again and drive away destroying your transmission. Many a BA Falcon owner has had this occur.
    A transmission specialist I spoke to some years ago when I enquired about the failure of the standard Falcon cooler, showed me three boxes that had been brought in for rebuild that week for that problem.
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