Help Me Understand This manual tcase/trans Leak Pattern

Hey guys,
My ‘99 has developed a slow leak from the transfer case/ transmission, and I am having some trouble pinpointing where and more importantly why.

The truck is a hunt vehicle, driven a few times a week around town during the off season. manual trans, fluids were changed 10 months ago, new oem crush washers, and plugs, redline Mt 90 fluid, new shift bushing, and everything torqued to spec.
a few hundred miles put on it at most, it’s mostly trailered.
I keep a catch sheet under it all year, so I know it hasn’t lost a single drop until now.

I first noticed the spotting last week, and on inspection I saw two slow drops forming off the transfer case shield. both the tcase drain plug and the trans drain plug appear tight and dry.
the best I could tell is that maybe I’m getting intermittent blow out from the trans vent as I see some residue there, although I could really see a path for the oil to make it to the t case shield.

I’m also not sure why there would be blow out from the vent at this point, the truck is lightly driven around town, and the drops first appeared after the truck has been sitting for more than a week.
We are in Az, so it just now started getting really hot, but this truck is garage kept.

I’m not really really sure where to start chasing on this, but I can’t let it slow drip without figuring it out. any thoughts?

 

I also noticed while under what looked like superficial crackling. These look like actual cracks in the pictures, but they felt only on the surface and were dry. Is this concerning?

T case drops and vent blow out residue. The vent blowout trail didn’t feel actively wet

 

forward of the transfer case. This mating block looked wet but was not.

 

You are 100% sure it is gear oil?

There would be no way any pressure would build up in either gear box and push out the vent.

In such cool temperatures .

Clean things off and see what happens .

 

and these were the crackling that I noticed while trying to take pictures of the vent run off

 

yeah its’ definitely gear oil. That’s what I thought too about the pressures since it’s been sitting in the garage. definitely had blow off from the vent at some point, but it doesn’t *seem* like that’s what could be seeping now

 

Maybe pull the shifter boot from the interior and try to get a better look from up top?

Breathers weren't clogged up with any dirt or debris were they?

 

went ahead and pulled it for pictures then degreased from top and bottom. I’m still not seeing anything more than seemingly old blowout from the vent. I drove it around for a few minutes and rolled it through 4high & low a few times then parked it on a fresh catch sheet, We’ll see what it looks like tomorrow

 

pictures from the top. I degreased and cleaned this area with a wire brush when I did the bushing replacement, which would have been probably last October. definitely got grimey quickly.

 

That looks real wet for having been cleaned last year and only have a few hundred miles put on since then

 

Wonder if your top shift seal is bad and seeping past it while driving but it takes awhile to make it down to the bottom of the case.

The cracks are just casting ''flaws'' and perfectly normal.

 

Agree, did the shifter gasket get replaced or sealed with RTV?

 

Thanks for the ideas. That’s interesting, I changed the gasket on the shifter when I replaced the shifter bushing for the trans, but the tcase had not been cracked open, so I left that gasket alone since I had some trouble finding the oem tcase gasket at the time.

I will get replacements for both and throw them on, that’s an easy first step

 

Sorry I got here late, but yeah it's definitely the paper gasket that has failed on the tcase. Mine did the same after like 20 years. Just scrape off the old paper gasket and reseal it with RTV and call it a day.

 

Well after all that I’m still getting a leak. Nothing else coming down from the top, but still building up fluid in the t-case protector. I took that off and after some looking I found the there is seepage from the seal where the front driveshaft enters the t case.
Any Ideas on how bad that is to replace the seal there?

 

Check to make sure your breathers are not plugged up/seized - pressure build up can cause oil to leak through the seals.

To answer your question, the job doesn't look too bad. It looks like you can do it with the transmission still installed. @turbodb @erice

https://www.tacomaworld.com/threads...t-gen-edition.138573/page-10854#post-28414154

 

Is your leak from the trans side or tcase? (the trans is more common). Best way to know is to fill them both to "flowing out of the fill hole" and then wait a month or so and see which one you need to add fluid to.

If you're leaking at the trans (which is where I had a leak), then the steps are pretty simple, and can be done with the trans in place: Replacing the Transmission Seal for the Transfer Case Input Shaft on a 1st gen Tacoma (or 3rd gen 4Runner) – ADVENTURETACO

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TurboDB, those are some great photos and nicely written guides! Bookmarked!!

 

Thanks for the information fellas. turbodb, that write up is unbelievably valuable. Thank you for putting that out there.

I will have to get the tcase protector off and have another look.
It looked to me like it was coming from the tcase front drive shaft. I marked it on one of Turbodb’s pictures.

I’m headed into the start of hunt season, so as long as it doesn’t start gushing oil I think I’ll wait and pull the whole trans after the season is over and have it rebuilt by Marlin or someone similar.

With my luck I would get halfway into pulling the tcase and have something catastrophic happen and kill my hunt season.

 

Ahh, gotcha; I misunderstood what you meant by "front driveshaft," and thought you were just calling the input shaft the front driveshaft. If that's where it's coming from, you may not need to pull the full t-case at all, as I think you can replace that seal with it still in place.

I definitely wouldn't worry about it very much if it's not really pouring out. Just keep an eye on the level and put in a few ounces as necessary until the weather warms up.