Trans fluid leak at vent tube by dipstick
 

2000 Blazer with 93k miles.

Transmission fluid leak at vent tube by dipstick. Researched around the site and found a discussion on an earlier year Blazer. Fast forwarding, I removed the upper plug on the transfer case. Fluid gushed out. After that, the fluid leak at the vent tube stopped. I'm guessing that there is a seal between the transmission and the transfer case that is leaking fluid from the transmission to the transfer case. Is that a correct assumption?

Also, I replaced the transfer case vacuum switch (under the battery on a 2000) in May. When I replaced it, I noticed that the vacuum switch contained transmission fluid. That was in May 2010. Other than being driven around the block once a week by a neighbor, the truck sat from May to now, October. So... there is transmission fluid in the vacuum system. I am guessing that that the vacuum system will purge itself over time. If not, what do you suggest?

As to the first issue, where is the seal I need to replace, and how much of a job is it?

Thanks for any replies. Rich

Transfer case input seal. The transfer case must be removed to change it.

Looks like I have the same issue..darn have not check t case fluid level yet

Swartlkk... thanks. I have a "just curious" question. The transfer case vacuum switch under the battery operates a cable. How does the transmission fluid get into the vacuum lines... I guess I'm asking where does the transmission fluid get into the vacuum lines?

Trans fluid gets into the vac lines through a leaking vacuum switch on the transfer case coupled with a leaking input seal which causes an over full condition in the transfer case. Normally, fluid would not get up around the vac switch.

Got it! Thanks. So while the transfer case is out for the seal job, it is wise to replace the transfer case vacuum switch whether is leaks or not.

Definitely. It is also a good time to clean the lines out. Trans fluid can cause some very pesky problems with the HVAC system if it is allowed to migrate all the way into the cab (which it can).

Does anyone have the better double lip replacement seal part number? Mine is a 2001 zr2..



Just pulled my case minutes ago and the seal was still intact but the t case did indeed have a TON of fluid in it!!:icon_doh: It was hard as a rock and pretty much just crumbled when I put my little screw driver in there to pry it out.. I ended up just pulling the input seal housing off and pushed it out from the inside.. So monday I will be ordering all the parts I need and was hoping someone would have a part number for the seal to make finding it a little bit easier

Replacing item 1 and 8?
 

You've mentioned that the seal and vacuum switch need to be replaced to repair the problem of the transfer case and/or the vacuum system filling with trans fluid. Are we talking items 1 and 8 on the attached image file? Thanks, Rich

Yes. The vacuum switch cannot pull fluid up and out of the transfer case if it were not over full of fluid due to a leaking input seal (#1). The switch (#8) has two o-rings in it that should seal it from being able to suck in any fluid. It takes the combination of these two items failing to allow fluid into the vacuum system.