Ok, this is a problem I have been dealing with for a while, actually since I bought the truck. After long periods of driving, or after a lot of stress on the tranny (i.e. driving through hills, off roading, or just slamming through the gears) ATF will come out of the breather tube that runs into the engine compartment, which of course dumps onto the exhaust manifold, causing smoke and what not. At first I thought it may have been because the people I bought it off of put too much ATF in, so I change the filter and put new fluid in, it still does it though. It doesn't appear to be a lot because my fluid level hasn't dropped enough to where I have to add more, but it's still annoying and worrysome. Anyone have a suggestion as to why this is happening? BTW, 98 Blazer 4x4.

 

Hey guys, hate having to bump a thread, but this is an issue I would like to solve, instead of having to constantly refill my tranny. Thanks

 

Your positive its your tranny vent tube?The only vent tubes that go into the engine compartment is the t-case and front differential.

That being said, if your losing tranny fluid, pull your t-case fill plug and see how much fluid comes out. If its just a dribble, good. If its a gusher your input seal on the t-case is shot and your tranny fluid is drianing into your t-case. Get that fixed asap, if not the vacuum switch fails and you end up with tranny fluid in your HVAC control system. That gets expensive.

 

Well, according to my Haynes manual it is the tranny tube, but that could be wrong, I've been told multiple thing with this tube, that it is tranny, t-case, and also that it is a vent tube that connects to both t-case and tranny. It comes on the passenger side of the vehicle, right along side the tranny dip stick, and has a little sponge on the end.

If it is my input seal how difficult would have be to change, I do not have a lot of tools, mainly stuff for routine maintinence and that's it. And how important is it to have it changed, it has actually been doing this for a year, and this is actually the first real response I have gotten on what it could be.

If it is going into the HVAC control system would there be any other symptoms? And how important would it be to get that fixed right away? Money is tight, and if I can I would like to put this off till I can get some more money, but if I can't then I gotta do what I gotta do.

Oh one last thing, I forgot to mention this, it has never spew tranny fluid one the outside temp drops below like 40. When it is cooler out, the problem goes away. And when I bought the vehicle it was doing this, but the tranny was overfilled, and filter and fluid change helped a lot, but it's still doing it. Just some additional info I forgot to put in.

BTW, thanks for responding, it's greatly appreciated.

 

There are 3 vacuum lines that run down to your t-case. One provides vacuum from the engine to operate the vacuum switch. The vacuum switch then has a vacuum line that goes from the t-case to the vacuum actuator (under the battery) which engages your front axle so you have 4x4. The third vacuum hose is a vent tube. It is hooked up to the t-case in two places and has a tee about 1' from either location to merge the two lines into one. That hose ends near the tranny dips stick tube with a piece of sponge on it to keep debris out, and the other two hoses should be zip tied to it and to the top tranny to engine mounting bolt. Real bear to see from any direction, buts its there. To find your tranny vent hose reach up on top of the tranny right behind the where the bellhousing meets the tranny case. Thevent hose out of hte tranny is roughly 4" long, GM stuck another piece on it that is longer, however that typicaly just hangs down the side of the tranny, and that is only on the newer trucks. If this is where you are leaking tranny fluid, thats OK provided your not low on fluid. However if your fluid level is fine and its spewing out, you may have other issues. Tranny fluid is cooled via cooler lines that run from the passengers sdie of hte tranny up to the radiator. If those lines are pinched or plugged your asking for trouble and a complete tranny rebuild. Heat is the number one reason trannies fail. Over heated fluid spewing forth is a indicator the fluid is getting to hot. Why is another question, and one you must find an answer to.

IF the fluid is coming out of the vent hose by the tranny dipstick tube, your t-case is too full of tranny fluid. To verify that you simple pull out the top fill plug and see how much if any fluid comes out. If it is a gusher you ahve problems with your input seal. To fix the $5 seal you need to replace it. That is pretty simple, you take the driveshafts out, disconnect the t-case, and then unbolt it from the tranny. Lower it to the ground and change the seal. Use some RTV to replace the gasket between the t-case and tranny adapter, reinstall. Fixed.

If the input seal is leaking it will eventually take out your vacuum system. Your HVAC system is connected to teh vacuum lines and this will cause you to lose control of your a/c and heating. This gets expensive to repair.

Post up some more information and we cna go from there. If you let this go, it could become real expensive real fast. Provided it realy is something to worry about.

One last thing.
The proper way to check the tranny fluid level is; drive the truck for 20 minuites, park on flat level ground and leave the engine running, pull the dipstick and check the fluid level. It takes one pint to go from the bottom of the cross hatch area to the top, add fluid accordingly.

 

Sorry it has been a little bit since I replied, but I have started college back up and it's been tough for me to get time to work on the blazer. I went to check the t-case, and, not to sound like a newbie, but I just was to make sure I am pulling the right plug before checking the t-case. Is the plug I want to take out on the back side of the case, to the driver side of the rear output shaft, and the plug that is higher? I just want to make sure, this a my commuter from school to home every other weekend and I can't be pulling the wrong plug out and messing something up. Thank you.

 

Yes, the top "plug" is where you add t-cse fluid. The bottom one is wherer you drain it. When you take out hte top one a little dribble of fluid should come out, if it pours out see my above posts.

 

Well.....I never got around to checking the transfer case, and as of now it has become the least important concern right now. The other day I was going home for the weekend from school. I got out on the highway and my vehicle started pulling really hard to the left, then would push back to the right. I got off on the next exit and as I was pulling into Burger King it gets really bad. SO, I get out and look under the front end to make sure that nothing broke up there, then head towards the back, and as I'm heading back there I see the problem, a lug snapped off on my driver side rear wheel. Not a big deal right, easy fix, so I make sure everything else is tight and head back to school to get my girlfriends car. While I'm sitting at the stop sign waiting to turn out of Burger King I look down at my tach, and my RPM's are jumping like crazy between 300 and 1200, which is exactly what it was doing this summer when I had to drop $1500 into the motor to get it running right agian. So now I have to get it towed back home (my dad has a trailer) to get this problem fixed. I'll probably have my mechanic take a look at the t-case when he is working on the engine. I have a few decisions to make. If it costs too much to get the engine fixed I may just put a new 4.3 in or even up to a 5.7. If that is not fiesable I may end up getting the 4.3 fixed, then, sell the thing, it has cost me too much money (I paid $4500 for it and am up to about $6000 in repairs) and I can get something more reliable. I love this truck, I have never been in something as comfortable as this vehicle, but it is just costing too much to keep it running.

 

I doubt your broken lug stud caused the drag to the left. More like a hanging caliper.

Your engine troubles might be caused by your tranny. Check that tranny fluid.

I forgot which year truck you have. I believesome of them had the MAP sensor hooked into the vacuum system. Your t-case is also tied into the vacuum system. Now if your t-case is full of tranny fluid, it could be venting into your vacuum system and your MAP could be getting false readings, thus throwing your puter off, and changing your rpms.

In short, your current engine trouble could still be related to your tranny. The pulling to one side is no doubt a hanging caliper or wheel bearing.

 

Hmm I never thought about the t-case problem messing with vacuum. I'll have to tell my mechanic about that idea.

I have a '98 btw.

The reason why I was pulling from side to side is because at the highway speeds the wheel was wobling