1. Welcome to Tacoma World!

    You are currently viewing as a guest! To get full-access, you need to register for a FREE account.

    As a registered member, you’ll be able to:
    • Participate in all Tacoma discussion topics
    • Communicate privately with other Tacoma owners from around the world
    • Post your own photos in our Members Gallery
    • Access all special features of the site

Auto Trans temps woes

Discussion in '1st Gen. Tacomas (1995-2004)' started by Svridge, Dec 1, 2023.

  1. Dec 1, 2023 at 3:49 PM
    #1
    Svridge

    Svridge [OP] Well-Known Member

    Joined:
    Jul 30, 2023
    Member:
    #430140
    Messages:
    87
    Gender:
    Male
    Ventura, California
    Vehicle:
    '99 Tacoma Extended Cab, 3.4l Pre-Runner
    Anybody able to tell me what's going on with my trans temps? I have an ultragauge hooked up to the obd port that I use to monitor the engine and trans temps and I'm not sure what's going on with the trans. Since I bought the truck and the UG, the trans would read roughly the same as the engine ~175° F. The problems would start when I go up hill. Even on a mild hill almost instantly the trans starts climbing up to 220+° if I don't slow way down. A couple days ago I used the truck to tow a boat around and since then the trans will only go up to 140°~ on flat ground and maybe ~160° up hill which I'm ok with being within operating temperature. The real kicker is that every now and again, it will go back to running hot. I drive up the same fairly steep 5 mile hill every day and one time it will stay below 160° and the next it's pushing 230°, as if the radiator isn't doing anything to cool it. I'm thinking of putting in a divorced transmission cooler but I also don't want too much cooling or preventing the trans from getting up to operating temperature, but I also don't want to keep driving around worried about burning up my transmission or driving 15 mph up hills
     
  2. Dec 1, 2023 at 4:00 PM
    #2
    Clearwater Bill

    Clearwater Bill Never answer an anonymous letter

    Joined:
    Oct 11, 2014
    Member:
    #140097
    Messages:
    24,830
    Gender:
    Male
    First Name:
    Billy
    Largo Florida
    Vehicle:
    '13 5 lug AC w/convenience package
    A few OE parts from fancy trucks
    You have an MX model?

    I found this

    upload_2023-12-1_18-59-22.png

    Just wanted to verify you have the gauge set up right before going after the transmission.
     
  3. Dec 1, 2023 at 4:19 PM
    #3
    jberry813

    jberry813 Professional Fluffer Moderator

    Joined:
    Jan 21, 2011
    Member:
    #49636
    Messages:
    28,484
    Gender:
    Male
    First Name:
    Jason
    Lake Tahoe
    Vehicle:
    2012 DCSB Sport
    ...too much shit to list.
    When is the last time you changed the fluid?

    To explain what is going on:

    ATF degrades with extreme heat cycles or just from being in the sump too long. As it degrades, ATF oxidizes which changes the dynamic coefficients of friction. Once that happens it can leave varnish deposits on the clutch faces, often referred to as glazing.

    The clutch plates and disks only cool down when you have ATF flow in and out of the clutch material and faces. Clutch disks are faced with a porous material of a cellulose fiber resin. That porous material allows oil to flow into it and squeezes some oil out during engagement. Once that varnish deposits allow a glaze to form, it prohibits cooling oil from flowing into or out of the porous material, and the ATF degrades even faster because of the flash temperature spikes.
     
    Madjik_Man and MalinoisDad like this.
  4. Dec 1, 2023 at 4:26 PM
    #4
    MalinoisDad

    MalinoisDad Misanthropic dog person

    Joined:
    Jul 16, 2017
    Member:
    #224205
    Messages:
    1,480
    Gender:
    Male
    First Name:
    Michael
    Vehicle:
    01 TRD PreRunner 5VZ
    5100s w/ 881s, JBA UCAs, J59s, other stuff and things
    For sure look into whether the readings are accurate or not. But, definitely look into the trans service history if you can.

    Drain and replace ATF fluid if you aren't sure of the service history - don't flush. Repeat as many times as seem to be needed. I went above and beyond and plumbed in an additional ATF cooler right behind my grill and an external ATF filter in line.

    Turn overdrive OFF for sustained hill climbs.
     
  5. Dec 1, 2023 at 4:32 PM
    #5
    O'Silver_Taco

    O'Silver_Taco Well-Known Member

    Joined:
    Aug 26, 2021
    Member:
    #375390
    Messages:
    4,238
    Gender:
    Male
    First Name:
    MD
    Vehicle:
    98 Dlx Sr5 ext AT Rwd
    3rz to 2Rz bebuilt block and new heads
    If you want it to last a long time.....gotta keep it cool....

    using the radiator to cool these as they reach seniors gets more risky....




    I'd recommend a moderate size cooler.....and an inline mag filter....Raybestos...
    and new gates hoses....the high heat is deteriorating them in double time....

    If you use new ATF....I'd recommend the LubeGuard additive as a safety net.......
    and save the old fluid.......just in case...

    I'd even pull the wire connectors....and use electronic cleaner.....or Deoxit...
    and then smear dielectric grease on them...


    could be that temp sensor has gone south....like the ECT coolant sensor when its toast...
    if that's so.....I'd really be worried....
     
    Last edited: Dec 2, 2023
  6. Dec 1, 2023 at 5:08 PM
    #6
    O'Silver_Taco

    O'Silver_Taco Well-Known Member

    Joined:
    Aug 26, 2021
    Member:
    #375390
    Messages:
    4,238
    Gender:
    Male
    First Name:
    MD
    Vehicle:
    98 Dlx Sr5 ext AT Rwd
    3rz to 2Rz bebuilt block and new heads
    That large over drive solenoid...ages and clogs over time.....
    if you disengage it when its real old.....you run the risk of it not kicking back in....
    thereby losing your over drive.....forever...or at least until its replaced....

    Old fluid and old rotting hoses speed all this up...



    This is my backup plan that I bought......just in case....

    https://www.ebay.com/itm/255655536375

    s-l1600 (2).jpg
     
    Last edited: Dec 2, 2023
    This site contains affiliate links for which the site may be compensated.
    #6
  7. Dec 1, 2023 at 7:38 PM
    #7
    Svridge

    Svridge [OP] Well-Known Member

    Joined:
    Jul 30, 2023
    Member:
    #430140
    Messages:
    87
    Gender:
    Male
    Ventura, California
    Vehicle:
    '99 Tacoma Extended Cab, 3.4l Pre-Runner
    Thanks for the replies, I have about a month to get this truck buttoned up before I ship out for the military...was already planning on dropping the pan and changing the filter next week, inline cooler and mag filter, and verifying the temp sensor is correct with my own meter. No issues with the transmission and the overdrive button works fine.
     
  8. Dec 2, 2023 at 5:06 PM
    #8
    Glamisman

    Glamisman Well-Known Member

    Joined:
    Oct 22, 2016
    Member:
    #200436
    Messages:
    4,993
    Gender:
    Male
    IMHO, it could be a few things. I will note them as they come to mind, they are not in diagnostics priority.

    The next time slow down enough to put her in manual second and watch the temps. Look at your fan clutch and see if it is free wheeling or if she needs replacing, I am assuming there is a fan shroud on the radiator and the radiator is in good shape.

    If there is not trans any slippage the torque convertor is THE biggest heat producer, any issues with that and she will need to be replaced. This diagnosis is best done by an experienced transmission person.
     
  9. Dec 2, 2023 at 7:04 PM
    #9
    tacoman2001$

    tacoman2001$ Well-Known Member

    Joined:
    Sep 23, 2022
    Member:
    #406478
    Messages:
    767
    Gender:
    Male
    I have 33s and a supercharger so it's very easy to overheat the trans. I got an external trans cooler and a gauge to monitor temps. If you find it runs too cold you can use cardboard or plastic to block it off to increase temps. I stay around 140F. up the same hill are you in the same gear? If the torque converter isn't locked or is beginning to slip going uphill it will create lots of heat fast.
     
  10. Dec 3, 2023 at 4:31 PM
    #10
    Svridge

    Svridge [OP] Well-Known Member

    Joined:
    Jul 30, 2023
    Member:
    #430140
    Messages:
    87
    Gender:
    Male
    Ventura, California
    Vehicle:
    '99 Tacoma Extended Cab, 3.4l Pre-Runner
    Going up it tries to hunt between 3 and 4 so I'll turn the overdrive off and try to play with the pedal to get the TC to lock up, it generates the most heat in 3rd. I'm going to change the filter and add some new fluid to see if that helps anything. If not I'll look into adding the cooler I have maybe with a thermal bypass valve to keep the temps normal
     
  11. Dec 3, 2023 at 4:38 PM
    #11
    tacoman2001$

    tacoman2001$ Well-Known Member

    Joined:
    Sep 23, 2022
    Member:
    #406478
    Messages:
    767
    Gender:
    Male
    Smart they I've you an O/D button so feel free to use it.
     

Products Discussed in

To Top