Ok, thoughts on an aftermarket trans cooler?

Discussion in 'Chevy Silverado Forum (GMC Sierra)' started by steved, Apr 8, 2013.

  1. steved

    steved Former Member

    OK, one of the forums I was on always encouraged adding a trans cooler; even if the truck was equipped with a factory cooler. Their explanation was the factory setup is inadequate. It didn't matter if the OP was having wiper issues, an aftermarket trans cooler would fix that too...

    I have been watching my trans temps just to see what I get too, and even loaded heavy (trailer pushing 10k pounds); the most I have seen to date is about 180*F. Most of the time it runs about 140* to 150* when just driving around. None of these temperatures seem high to me? I want to remember the trans warning light is preset at 235*F?

    So my question is this, if the trans isn't running hot; why would you need to add another cooler?
  2. Sierraowner5.3

    Sierraowner5.3 New Member

    to a point, the cooler it runs the longer life you get out of the transmission. im not to good on stuff like this, im sure someone else will chime in.

    Alex
  3. steved

    steved Former Member


    I agree with that to a point; but there is also a point they don't run hot enough, and that causes poor economy and condensation buildup.
  4. tbplus10

    tbplus10 Super Moderator

    To an extent I agree with that other site if its to cold your trans will sometimes act funny by not shifting or shifting to early so I believe you could over cool a trans in very cold weather.
    A perfect trans cooling system would be a secondary cooler that opened at a preset temp and was only open as long as the temp remained above that temp then closed when temps cooled.
    By adding an aux trans cooler youll never know if you kept temps down youll just have to assume its doing its job sometimes its better to not know what wouldve or couldve happened.
  5. SurrealOne

    SurrealOne Former Member

    Funny Answer: Fat chicks:lol:

    Real Answer: Towing or hauling heavy loads, especially in hilly terrain. (Kinda related to the funny answer, I suppose. :glasses:)

    Seriously:
    Your daily use may run cool. Then one day let's say you decide to tow/haul something at or near your max capacity ... and you are doing it in the mountains. You won't be seeing your usual tranny temps on THAT day ... and you may even get to see your tranny temp warning light depending on the load you have, the grade you're on, and the duration for which you're on it. THAT is the day where the cooler is invaluable.

    For those whose trucks are glorified grocery getters, an additional or upsized cooler is probably irrelevant unless they are running for long periods in the Arizona heat or something. But for those who use their trucks to tow/haul, an additional or upsized cooler MAY make sense ... based on a combination of load and terrain, of course.

    @tbplus10, umm, I believe the cold weather bypass exists to prevent the kind of weirdness you mentioned in cold weather. Are you suggesting the trans acts funny even with a cold weather bypass in place? (It doesn't get stupidly cold, here, so I wouldn't know.)
    Last edited: Apr 8, 2013
  6. steved

    steved Former Member

    I understand that...but I have temperatures towing against the max GCVW for this truck, in mountainous terrain; and it never got much hotter than 180*.
  7. SurrealOne

    SurrealOne Former Member

    Ahh, in your original post you didn't mention that the 180* was at max load. Given this, I wouldn't sweat it. People doing it in 100 degree weather across the steeper grades of the rockies may have a different experience and, thus, a different need, than someone in the cooler climate and gentler grades of the appalachians.
    Last edited: Apr 8, 2013
  8. j cat

    j cat Active Member

    with synthetic fluids used today in these transmissions like GM DEXRON VI under 190 deg f you will have no fluid damage.

    years ago with DEXRON III keeping the temp as low as possible did help since DEXRON III quickly breaks down and causes acid damage to the valves and clutches .
  9. tbplus10

    tbplus10 Super Moderator

    Yep even with the bypass in cold weather (below 0 deg) if the trans had been cold soaked like maybe setting over night they act a little funny until temps get warmed up. And as you know external temps will affect how long the warm up takes. I dont have the problem down here in Texas either but I have had the chance to experience it on a few buis. trips to cold climates last winter.
  10. j cat

    j cat Active Member

    the acting funny when very cold like 6 deg f is when I first saw the synthetic fluid performance compared to the dexron III in my 2000 SILVERADO during the winter of 2001-02 .

    synthetic works great when the very cold weather hits. faster engagement and less slipping [acting funny].......
  11. tbplus10

    tbplus10 Super Moderator

    I agree synthetic vs conventional fluids is a big difference in cold or warm weather operations I dont know Dextrons temp range I do know at one time in military vehicles it was the only extreme cold weather recommended trans fluid for any mfg vehicle. Not sure if that still holds true.
  12. steved

    steved Former Member

    There are a lot of hydraulic systems that spec ATF if the temps are supposed to get really cold. This truck (read: transmission) won't even break 90*F if its really cold unless your running slow and the converter unlocks a lot. I've noted that it won't lock the converter until the trans reaches about 70*F.

    Isn't Dex6 a thinner synthetic ATF when compared to Dex3? I'm probably going to do a pan drop when the time comes...not really sure what I'll use. I've already had to add to it (mystery fluid disappearance), and used Castrol Dex6. Probably hook up with the local Amsoil guy and see what he can do for me.

    On a side note, I scored a new/unopened 5-gallon pail of Amsoil 75w140 SVO a few weeks back for $50...gotta love Craigslist.
  13. j cat

    j cat Active Member

    DEXRON VI is a slightly lower viscosity fluid. very close to the toyota transmission fluid they have used for many years. I believe that cold weather with the DEXRON III does cause slippage . with these newer transmissions it is true that if the fluid does not get hot enough you will get the delayed up shifting . with older vehicles that do not have this type control you will not have this effect.

    one thing I did notice with a very large cooler on my 1984 was in the winter the tranny cooler caused the engine to run too cool and I lost some heat out of the heater. I had to block 50% of the radiator to get my toes warmed up in the below 20 deg f temps.

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