Transfer Case vent plug leak

New guy here in search of answers. I searched the history but couldn’t find a similar issue. I have a 91 V6 3.0 Automatic 4 wheel drive with a HUGE transmission fluid leak coming from the transfer case vent plug. Originally I thought it was rear driveshaft input seal so I changed that. Started it up and out came the fluid again.

This started today when I got it in to drive. It wouldn’t engage in first until I would rev it up a bit and then it would engage and go (that’s been a thing since I bought the car two months ago). The further I drove the more it wasn’t engaging and the higher I had to rev it in order for it to catch and go. I pulled over and saw the leak happening then. I knew I was loosing fluid and loosing it fast so I drove it the half mile home. Made it about 100 feet from my driveway and it wasn’t moving any further. I pushed it the rest of the way and then went and got the seal. Changed that, added some fluid, started it up and it immediately started leaking. Leaving it running I looked under it and saw it coming from the vent plug.

Is this a internal seal that has shit the bed causing increased pressure or allowing fluid to get where it’s not suppose to be? Or can the vent plug simply go bad and allow a mass loss in fluid?

The guy I bought it from said he thinks the torque converter was going out because sometimes it wouldn’t engage in first and would move forward when stopped at a light. I drove it and it would come in and out of engagement when sitting at a light. Once it would engage it would drive fine and shift just fine. He changed all the solenoids so I figured he just didn’t fill the transmission properly after that since it’s symptoms seemed like a fluid issue since it would only happen when stopped at a light. I believe I gave enough details for some insightful replies. Any help is greatly appreciated.

 

No one is responding because there's little anyone can help you with. It sounds like the trans is toast, and the trans fluid 'vent' leak may be due to fluid overfill.....that's just a wild ass guess. Your best bet would be to consult a transmission specialist. This is just my opinion....nothing more nothing less. Good luck to you, sir.

 

Many years ago on my 92 I had a bad leak coming from the vent when I would go over 60 mph. The tranny light came on and I pulled over. Got it towed to a dealership nearby and they couldn't find anything wrong but told me to not go over 60. It was fine all the way home. I took it to a local dealer and told them what happened. They finally found that some line had been kinked and that caused it the fluid to over heat, expand and spill out the overflow. That was 16 years ago so I can't remember exactly which line or tube the found but I never had the issue again. May be that something is causing your fluid to not circulate thus overheating. Hope this helps.

 

UPDATE:

I tore into the transmission to figure out the cause of my problems. Come to find out there’s a planetary gear set and two sets of clutches in the transfer case. The transmission and transfer case are essentially one unit that all share but don’t share fluid. I meticulously pulled everything out and got to the transmission front support. The brass bushing and piston ring seal were worn out pretty bad on the front support and direct drum. I sourced the parts for the bushing but the piston rings are not available anywhere. I ended up finding a remanufactured transmission local to me so I bought that. I’m having issues with that now, but I believe it’s electrical. Anyways, if you need help tearing open your transfer case, I’m pretty well versed now unfortunately.

 

Thanks for the update and keep us posted

 

Taking that apart yourself is one hell of an undertaking. I don't know if I could commit to that.

If you had fluid coming from the vent there are a few reasons possible that I know of. 1) Overheating fluid as per one of the previous replies 2) aerated fluid.

Fluid can be aerated from too low of a fluid level - air then gets sucked through the pump and into the fluid passages/channels and foams up so bad it starts spewing out the vent. Or too much fluid which then gets aerated by the planetary gearsets spinning around and you get the same result. But with the overfill scenario I think you get other issues like bad shifting, and noises, etc.

I'm no expert and I don't know jack $h!t about transmissions, so take my comment with a grain of salt. Heck I don't even know why I'm commenting.

 

Yeah I wish it was an issue of too little or too much fluid. In my case, it was bigger than that. The transmission pump was pumping fluid and it was getting past the seal, then into the trans case and over filling that and pouring from the vent plug. The fluid coming out of that was perfect fluid and it would leak from the vent as soon as I started the car in the morning.