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A343F automatic transmission pan gasket leak

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  • A343F automatic transmission pan gasket leak

    Hi guys,

    Long story short, I am sick of my trailer getting a fine coating of ATF each time I tow it, so I want to replace the pan gasket of my transmission. I am confident the pan gasket is at fault here - it does not look like it's on right, the cork is bulging out at points and not at others. I have had dramas with that since I got the filter replaced in March. I have lost all confidence in the place that did it, so I don't want to take it back there.

    What's your thoughts on using either another cork gasket or an alternative like RTV sealant? I don't care too much myself, I just want it not to leak.

    I am thinking it should be fairly simple to replace as it was off in March to do a auto trans filter replacement so the bolts for the exhaust should not be too badly corroded into place, plus they have had a bath in ATF. Does anyone else agree or would this be insane for an amateur home mechanic to do?

    My Prado is a 2000 petrol 3.4L VZJ95R.


    Last edited by RedAdventureWagon; 25-11-2019, 11:40 AM.

  • #2
    Sounds like someone overtightened the bolts.
    Cork is the right gasket to use but it will never work if the pan surface has been pulled due to over tightening of the bolts.
    Only option is to drop the pan and panel beat the surface true using a block of timber on a suitable bench.
    I always check my pan and give any bolt areas a touch up if they show signs of pull.
    Also check the dipstick "O" ring is sealing properly.
    When you refit the pan, tighten each bolt evenly as you go round the perimeter. No need for crazy torque, most old time trany men will use a 1/4" speed brace, one handed to get a feel for how tight things are.
    Pick up a rattle gun and you'd be shown the door.


    • #3
      Goodness only knows what the original guy did - half were loose and half were tight but I don't know how tight. Second guy I took it to did tighten them all up but using a normal hand wrench not a rattle gun! I have a torque wrench and would definitely use it for this job. Have you done this on this model of Prado carco and if so do you need to remove the sway bar from the body as well as the exhaust section?


      • #4
        Mine was diesel, so dead simple.
        V6 will need the exhaust cross over pipe removed which can be a real drama if rusted.
        But dropping the pan, changing filter and so on is a piece of cake. Much easier than the later models without dipsticks!
        Doesn't take full synthetic oil either which saves you a lot of $$$.


        • #5
          yeah probably overtightened some distorting the pan. Hardest part is getting the cross over pipe off. I haven't done mine yet as my pipe is just about completely rooted. I'll change the trans filter when the exhaust finally rusts out. And yes these things are a piece of cake to service.


          • #6
            Thanks for the replies guys I have had another look underneath, I have decided that whilst I could probably do it, it would likely take me all day; my son would lose interest in a longer job (he is 6) and I would rather spend the time with him. I had a call round a couple of transmission shops and have booked my Prado in for a transmission service (which will include the pan gasket) for next week. I will let you know how it goes. Will try and clean the underside up this weekend though.


            • #7
              Bad news guys. Trans guy said it's leaking from the bell housing. Possibly a front pump seal. Booked in for full gearbox out diagnosis next Monday


              • #8
                Final update on this guys, took it to another specialist and he diagnosed a leak through the pan gasket and possibly the breather. Luckily not a tranny out job this time, just needed a service, re-seal and refill. The specialist said it looked in very good condition inside which is good news. He did say there was a minor engine oil leak at the half moons (which I think is a factory standard feature of the 5VZ-FE) but I am going to keep an eye on this, I don't have the time or money to fix it now. I will keep an eye on the oil though of course.

                He did suggest fitting a transmission cooler in addition to the OEM radiator cooler given I do use this for towing, so I will get that done in the new year.


                • #9
                  Clean the half moons up and smear some ultra black around them. Easy fixed.... oh and dont forget to do the cam plugs too!