1997 chevrolet blazer LS 4x4. I just rebuilt my whole engine compartment...running good and i took it out 4x4 in the desert...came home and there was a vacuum line dragging from the top of the trans. I know there are 3 from the trans case. One goes froms trans to under the battery to engage 4x4. The other goes to wiper motor. The one I need to hook back up...a complete mystery. Mechanics couldn't figure it out either. I have a screw into the hose now because it looks like some fluid is coming out a little...(NOT TRANS FLUID) Seems like the tranns runs great still...IM LOST! Im a rookie in the gear head game. Can somebody look under there model and see what they see. I gotta get this taken care of to ease my mind. PS this is the very last thing I need to complete to call this overhaul 100% done!!! Thanks!!!

 

The three lines off the switch on the transfer case are the vacuum supply from the engine (what you state goes to the wiper motor), the one that goes to under the battery, and then a vent. The vent will run up to the transmission dip stick tube and just be strapped to the tube. This is likely the line you are talking about. It should not have any vacuum to it, but will vent a bit of vacuum when you disengage the 4wd system. It should also T into the vent from the top of the transfer case.

The fluid that is in the line is probably transmission fluid, but may look different if it has mixed in with the transfer case fluid (transmission fluid also, but may look different due to age,etc). I would recommend that you pull the fill plug from the back of the transfer case to check for an over full condition. This can result from a bad front input seal on the transfer case which would allow transmission fluid to migrate into the transfer case, overfilling it.

 

Kyle pretty well covered it.
There is a tube on the top of the tranny just behind the bellhousing. This is the tranny vent tube and if your tranny fluid gets too hot it vetns out this tube. This is also a place for dirt/water to enter the tranny. Generally this tube is about 4" long, however on my '00 GM did install an extension, vacuum hose same as the other vacuum hose ont eh truck.

4x4 in the desert could lead to excessive heat in the tranny. I HIGHLY recommend an auxilary cooler, tranny temp gage, and tranny pan drain plug. Auxillary cooler will help keep it cooler, temp gage will let you know wwhen the tranny is getting too hot, and the drain plug for preventive maintenance, drain and fill at least once per year, more frequent if you drive in extreme conditions or get the tranny too hot.

HEAT is the #1 REASONS TRANNY FAIL!!!!!!!!!!!!!!!!!!!

Heat cooks the gasekts/seals causeing them to leak, leaks cause slipping, slipping causes more heat, repeat.
Don't get into that visious cycle. Keep it cool!!!!
There is a rule of thumb, for every 10 degrees over 190 you lose 10,000 miles off the life of the tranny.

 

There is a vacuum ball located on the top of your hood. maybe from there ...the ball has somthing to do with your emissions. not shure but mine broke and i have put a screw in the line also.

 

The ball is a reservoir for the vacuum operated accessories (4wd front axle engagement & HVAC operation) and is not used for emissions.

 

Thanks guys! I havnt had internet but I ended up at a pic in part in california. I tracked the 3 lines and you were right. Just the transfer case vent tube that attaches to the tranny dipstick. It had a breather cap on it but it mustve fallen out while it was dragging. It was lower than the transfer case when dragging so it makes sense that fluid was bubbling out. Thanks a lot guys!!