Gasket needed between transfer case and transmission?

Discussion in 'GM Powertrain' started by Family Force 6, Jan 23, 2013.

  1. Family Force 6

    Family Force 6 Rockstar 100 Posts

    Well, my transfer case swap nightmare continues.
    The story: my NP246 TC was making noise, found a "remanufactured" one on CL for $500. Installed and thought I was good to go. First snow comes and 4WD is not working. Then starts making a bunch of racket. It's my wife's daily driver and I don't have time to mess with it so I find a guy "with 20+ years of experience at AAMCO" who says he'll pull the case and replace whatever needs replaced for $300-$700. However after looking at it he tells me that nothing in the case can be saved (he says the oil line fell out of the pump) and will have to find a builder case. He calls back and says he found a case that was rebuilt recently then the truck was totaled. He'll install it and give a one year warranty for $850 (of course it then turns in to $900 when I go to pick it up).

    I get it home and notice transmission fluid is leaking. I get under the car and can see that its leaking where the TC mates to the transmission and there is no gasket installed. Then I decide to check the TC oil while I have it on ramps. Pull the fill plug and it seems low on fluid. I pull the drain plug and the fluid (red tranny fluid, not AutoTrak fluid) is dark and cloudy- this is after 4 DAYS!

    I'm pretty upset at this point and go back to the shop to talk to him. I tell him it's leaking because he didn't install a gasket. He tells me that it is a "dry" connection between the TC and transmission and that no gasket is needed. Is that right? I thought the back of the transmission (it's a 4L60) was open and that a little tranny fluid get's in that connection. Who's right? Do you need a gasket there (it's a paper gasket from the dealership).

    He's still claiming he cracked open the case and installed new fluid but said he would drop the case and look at it to see what's going on. I also asked him about using autotrak. He said that he adds the friction additive directly to the tranny fluid and that its the same stuff, just cheaper. Thanks!
  2. Family Force 6

    Family Force 6 Rockstar 100 Posts

    Can anyone verify that lack of the paper gasket between the transfer case and transmission will result in transmission fluid leak? I'm supposed to see the "transmission expert" tomorrow and I'd like to be a little more sure of myself.
  3. Boonduff

    Boonduff Rockstar 4 Years 100 Posts

    The guy is right about there being no gasket between the tranny and the transfercase. It is a dry connection with the tranny having a output seal and the case having a input seal. But, he's wrong about the fluid.
  4. Family Force 6

    Family Force 6 Rockstar 100 Posts

    Thanks for the reply Boonduff. Are you 100% sure about that? He did install the GM stealership $10 gasket between the TC and the tranny and it stopped leaking (of course then the front output shaft seal on the TC started leaking because it wasn't seated all the way- this has been a NIGHTMARE).

    I've seen other threads that say that there is a bit of transmission fluid that spills when you separate the two and that was my experience when I originally swapped the TC (I know it was tranny fluid then because it was red and the tc had the proper blue auto-trac fluid). Even if the rear output seal on the tranny is letting fluid through, is that going to be a problem if I leave it like that or do I need to drop the tc (AGAIN) and replace the tranny seal?
  5. Toymyster

    Toymyster Rockstar 100 Posts

    I'm sorry to hear about your project turning to a nightmare.
    There is a gasket between the trans and the TC, but there should be no fluid in between. If you had fluid leaking between the two, either your rear trans seal or front TC seal are leaking. As long as he is willing to stand behind his work, there should be no problems. Good luck and I hope this helps.
  6. Family Force 6

    Family Force 6 Rockstar 100 Posts

    Been doing a little more research on this, just because I need to know before I move on from this learning experience.
    Not trying to be difficult, but I'm finding some other forum posts that are saying that there is not a rear transmission seal, like here (the postby daveiroc, who says he is an ASE certified mechanic, says there is no rear seal on the 4L60E 4X4 application). I've done a few searches on GMTC but haven't found anything (though I often have difficulty doing searches well on this forum for some reason).
    Can anyone else confirm if there is a rear seal on the transmission for 4X4?
  7. Toymyster

    Toymyster Rockstar 100 Posts

    I just got done putting a 4L60E trans in my truck, and I can tell you first hand, there is an output shaft seal, since I got a good look at it. And there is a seal on the input shaft of your transfer case. Otherwise you could not run different fluids in your trans and your TC, also there would be no need for separate fills and drains. Sometimes, mechanics can act like doctors, we all have differing opinions and ASE certs to stake our opinion on.

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