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Pulled the trigger on a transmission cooler

Discussion in 'Towing & Hauling' started by Dallas007, Apr 4, 2021.

  1. Apr 4, 2021 at 5:28 AM
    #1
    Dallas007

    Dallas007 [OP] New Member

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    I’ve read about every post on every forum about transmission coolers. As many others, I was surprised when I purchased recently my 2021 Tundra Pro Max that my $54,000 didn’t include a true transmission cooler. Upon installing a scan gauge I found my temps running 200-205 driving to Walmart. The thing that convinced me was two weeks ago I pulled my ATV over 4,000 miles in my wife’s 2 door, V-6 engine, Jeep JK. Lots of steep grades, 50+ mph headwinds, 80+ degree temperatures and that Jeep’s transmission fluid never ever went over 170 degrees. Jeep has a cooler. Nick is building a cooler for me and while I hated to spend the $$$, I’m convinced it will help my new truck to be around a bit longer. My intention with this post is to just share my own experience.
    Dave
     
    Last edited: Apr 4, 2021
  2. Apr 4, 2021 at 5:37 AM
    #2
    timsp8

    timsp8 Former Tundra owner for 13 years

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    I’d probably do it too if I had at 19+, but Toyota designs these transmissions to run around 185-195. There is a “puck” that has coolant running to the trans so theoretically atf will be close to coolant temps. I say this cause you compared it to a jeep. Constant temps under 170 in a tundra is bad.

    Anyway, post some pics.
     
    snivilous likes this.
  3. Apr 4, 2021 at 7:15 AM
    #3
    JohnLakeman

    JohnLakeman Burning Internet Daylight

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    This is not a decision you will live to regret. The financial pain (<$1000) will only hurt for a little while. You'll probably be making payments near that magnitude for 60-72 months.

    Fluid temps as high as 200-205 running to Walmart should be considered normal, with or without a thermostatically controlled cooler. Above 210, or below 185, for long periods should be considered out of range with a thermostat controlled auxiliary cooler, but possibly explainable due to extreme loading or pinned thermostat. In other words, remove the pin after installation, and leave it unpinned except to change fluid and check fluid level.

    If your towing conditions cause fluid temps to exceed 230+ (with the cooler), I would plan on close fluid condition monitoring and possibly more frequent fluid changes.
     
  4. Apr 4, 2021 at 8:28 AM
    #4
    sask3m

    sask3m New Member

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    My 19 was seeing 210 just driving around empty, after installing a cooler it's consistently at 185 empty.
     
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  5. Apr 4, 2021 at 8:30 AM
    #5
    SShooterZ

    SShooterZ New Member

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    I’m right about the same on my ‘19 Sequoia.
     
  6. Apr 4, 2021 at 9:08 AM
    #6
    JohnLakeman

    JohnLakeman Burning Internet Daylight

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    What is your coolant temperature running when the fluid is at 185?
     
  7. Apr 4, 2021 at 5:08 PM
    #7
    Dallas007

    Dallas007 [OP] New Member

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    I would be VERY happy with those numbers post-installation of the cooler. I appreciate all the feedback.
    Dave
     
  8. Apr 5, 2021 at 8:37 AM
    #8
    sask3m

    sask3m New Member

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    It runs somewhere in the 195-205 range depending on the outside temp. Haven't driven it a lot lately so that's kind of from memory but I don't think it changed much from before installing the cooler.
     
    JohnLakeman[QUOTED] likes this.
  9. Apr 5, 2021 at 8:54 AM
    #9
    Terndrerrr

    Terndrerrr guzzling dealer repellent

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    I’ve been watching my temps every time I drive. Last trip I took across town was 11 miles, mostly highway. Took 17 minutes. When I arrived at my destination, my pan temp had reached 180.6ºF. By contrast, my engine coolant temp had reached 192.2ºF after a few miles.

    Similarly, when my pan reaches low- to mid-190s and the t-stat opens up, this usually brings pan temps immediately back down to around 180ºF or even a bit lower, and it again takes a very long time if I’m just driving normally unloaded for the pan to get back up to engine coolant temps (which stay around 190ºF for me).

    Is the goal of the puck to bring trans temps up/down to engine coolant temps and keep them there? How far off can it be and for how long before it is deemed ineffective? Under what load and within what timeline is it supposed to be able to do this job? With everyone’s temp stories and my own observations, it appears the puck is not very effective, both with AND without an ext cooler.
     
  10. Apr 5, 2021 at 10:44 AM
    #10
    SShooterZ

    SShooterZ New Member

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    Again, very similar. Was flogging on mine a bit yesterday driving to my parents for Easter. ~140 miles round trip. Hottest I saw on the trans was maybe 195*, mostly 185-190*. Coolant temp for the most part was always at least a few degrees warmer and for the most part was near 200* +/- 5*.
     
  11. Apr 5, 2021 at 11:38 AM
    #11
    JohnLakeman

    JohnLakeman Burning Internet Daylight

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    The reason I asked was to try and understand exactly how the OEM transmission thermostat works. Note that I have the A760 transmission, which has a different thermostat, but I would expect the design parameters to be the same.

    Based on my temp observations in Texas, I thought the thermostat operated instantly open/closed, i.e. a very narrow temperature range for "phase change" of the wax element. My temps constantly oscillate over a narrow range (185-210), which would indicate the thermostat opening and closing to maintain the design set points. My observations are also made in hilly terrain, at highway speeds, with plenty of shifting, locking and unlocking; no hanging out in 5th or 6th for me.

    @sask3m Your steady transmission fluid temperatures indicate that your thermostat is reaching an equilibrium point part way between the "open" and "closed", and if my estimate of about 185 ( :notsure: ) as the closing point is correct, then your thermostat is "barely lifted off the seat". I was skeptical until I did a little more research.

    To avoid getting too far into the weeds, I will simply say that my original theory of instantly open/close thermostat is incorrect, at least for the AB60 transmission. The wax used in the thermostat expands when it melts, and causes the mechanism inside the thermostat to open. This "expansion wax" can be engineered to expand over a range of temperature that slowly opens the thermostat. This type of operation could establish an equilibrium position that diverts just the right amount of fluid to the cooler to maintain a constant pan temperature.

    The way the thermostat works is fluid flows first from transmission through the thermostat where high fluid temp melts the wax element to the degree the temp determines. The thermostat opens allowing fluid to flow to the cooler. In @sask3m case, the fluid is subcooled to a temp below the desired temp.

    The subcooled fluid then passes back to, and through the "hockey puck", where it warmed to a temp below coolant temp (puck is losing the battle). The rewarmed fluid then returns to the "back side" of the thermostat before returning to the transmission. On the "back side" of the thermostat, the fluid contacts the wax element case, and readjusts the degree of melting and the valve position. This happens continually until equilibrium is reached. I will still study why mine doesn't work that way. Maybe my thermostat has different design criteria; i.e., narrow temp range.

    I found an interesting YouTube video that illustrates this expansion wax mechanism (also used in some engine thermostats). The thermostatic element in the video looks almost identical to the diagrams I've seen of the OEM transmission thermostat, but it's using an electric heating element instead of fluid for the heating. This is an accelerated video, but it's still like watching ice melt. The best way to see the action is to watch the collar on the upper stem, and click along the time line at intervals:

    https://www.youtube.com/watch?v=0ZWcTHY2T0U
     
    Last edited: Apr 5, 2021
    sask3m[QUOTED] and WBW like this.
  12. Apr 5, 2021 at 8:11 PM
    #12
    sask3m

    sask3m New Member

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    As long as it keeps doing whatever it's doing I'm happy.:thumbsup:
    I don't get that steady kind of temp while towing though, with hills and such.
     
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  13. Apr 6, 2021 at 11:25 AM
    #13
    co2owen

    co2owen New Member

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    Mine got the hottest I've seen it get on Saturday. It was unloaded and not pulling anything. We were on country backroads (~65 degree day) and it regularly got above 240 degrees at the TC on fairly steep and long inclines at 25mph and under. Here's a snapshot.
    IMG_0082.jpg
     
  14. Apr 6, 2021 at 1:08 PM
    #14
    timsp8

    timsp8 Former Tundra owner for 13 years

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    TC will bounce up and down. Pan isn’t too bad for what Toyota says is normal. Why is your alt only charging at 13.1v?
     
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  15. Apr 8, 2021 at 11:21 AM
    #15
    co2owen

    co2owen New Member

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    Thanks timsp8. Maybe the TC temp is no cause for concern but it seems like it could get a lot higher while towing or hauling. I'll test it out this summer. I'll also be monitoring my Pan temps this summer to see how it behaves on hot days.

    The first time I used the OBD Fusion App, that 13.1v stood out to me too. It generally fluctuates between 13.0 and 13.3. Last time I measured, I was at 13.7 - 13.9 across the terminals while running so I'm not concerned. The dash needle sits right at 14v.
     

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