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Check/Change Your Transmission and Differential Fluids

manyman297manyman297 Member Posts: 1,254
in Trailer & Towing
How often are you all checking and/or changing you transmission, diff and transfer case fluids on your tow vehicle? I feel like not much is mentioned about how important this is. I just recently swapped all of the fluids on our truck at 40k. Front and rear diff fluid was dirty and definitely needed changing. Transfer case was surprisingly clean looking and the transmission fluid was a bit on the dark side. 

With the "lifetime" fluids manufacturers like to push, I'm not convinced it's a good idea to ignore it. My Tacoma has specific intervals for the diff and transfer case but simply says to check the transmission fluid. I'm glad I did a drain/fill on ours and will probably do it again in 30k miles.

Anyway, just curious if anybody else is doing this.
2021 400 BD
2020 Tacoma TRD Off-Road 
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    YanniLazarusYanniLazarus Member Posts: 354
    Toyota has a maintenance schedule for "special operating conditions" (includes towing) for our RAV4 Adventure which includes lots of additional fluid changes and more frequent service.  Funny thing is, our toyota dealer was unaware of this! 
    Yanni Lazarus 2020 T@B320S, 2018 RAV4 Adventure, Central CT
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    manyman297manyman297 Member Posts: 1,254
    We tow about 25% of the total miles on the truck so I split the difference and do fluid changes in between severe and normal maintenance schedules. 
    2021 400 BD
    2020 Tacoma TRD Off-Road 
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    berggerbergger Moderator Posts: 1,067
    Every 30k and I change them.  
    2021 T@b 400 BD  "Vixen Gail" 
    2018 Nissan Titan Pro 4X "Big Bird"
    Leadville Colorado
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    Maxcamp8Maxcamp8 Member Posts: 231
    edited May 19
    Another suggestion if you are towing with an automatic transmission truck:
    $300 ScanGauge III* plugs into OBD port and is easily set to show various fluid temperatures, engine torque, (and what gear you are actually in which truck does not show.)  I always had Manuals and drove drove by tach and engine sound, and now by Torque.  Towing I find am always in Fourth on a 6 speed Auto.  Toyota recommends never towing in Drive, always use the manual mode.  On this Auto lacking a Tow mode I am always in ECM mode which reduces the shift points slightly anyway.
    (*Avoid the older ScanGauge II as the manual settings of parameters can be unproductive and literally take several hours of trial and error.)

    Finding a reliable oil change place on the road can be a challenge and time consuming.  I long ago ditched the idea of quick change places that strip and damage your hardware.
    For our first trip in this new truck, I'd installed a Fumitomo (wrenchless) oil pan drain plug and brought the materials for self field change.  After 2600 miles our new oil was quite noticeably darkened.

    Toyota World forum has years of posts up to present about factory failing to correctly fill Automatic Transmissions.  Apparently the transmission cooler circuit by a third party factory should come prefilled with fluid and often did not.  Many folks were a bit low when they topped up.
    At 15K will check all gear fluids and auto transmission.  Plan to swap out by 30K given the towing we are doing.



    2021 T@B 320S Boondock/ 2012 Tacoma 4 cylinder truck / 2023 Tacoma 6 cyl. truck

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    manyman297manyman297 Member Posts: 1,254
    Once always used a generic Bluetooth OBD-II coupled with Car Scanner App to monitor temps. Works well and I just used it to perform a drain/fill on the Tacoma’s transmission a few weeks ago (have to get the fluid up to a certain temp to check the level.

    My transmission seemed to be filled correctly but I have read about people having underfilled transmissions.

    I’ve considered the Fumitomo valve but am paranoid for probably irrational reasons about it failing. 
    2021 400 BD
    2020 Tacoma TRD Off-Road 
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