Hello all, I'm new to the forum and have a little question.
The transmission on my 1995 Blazer LT 4x4 leaks transmission fluide from the vent tube. The transmission shifts just fine, not overfilled, no discolored or burnt fluide. What could be the reason for this?
Can't afford a trany rebuild at the moment, so need to find a fix for this.

 

Is this the vent tube at the firewall near the transmission dip stick tube or the one on the transmission under the truck? The one on the transmission is not connected to anything. The breather that is near the dip stick tube for the trans is actually the vent for the transfer case vacuum switch.

If it is the breather near the dip stick tube, then the problem is your transfer case input seal is leaking transmission fluid into the transfer case and, coupled with a leaking vacuum switch, is pushing fluid up into the vent line. The problem with this possibility is that you most likely will have transmission fluid throughout the vacuum system as well...

Please clarify where it is leaking from.

 

Thanks for the reply

Yes the fluid is coming from the breather tube next to the dip stick.
Is there a way for me to check for transmission fluid in the vacuum system? Will this be the entire vacuum system, or are there separate vacuum lines for the transfer case? I put it in to four wheel drive earlier today, and had no problems. Shifted in and out without problems, and it ran just fine.
What will I have to replace to fix this and how difficult is it?
I have just restored a Blazer K5 1984 from the frame up, so I do think I got the skills, if I just could find the problem and a walktrough

One more thing, what transfer case is in this truck? Is the transmission case a 4L60E?

 

Transmission is the 4L60E.

Transfer case is a NP or NV 233. I believe that both New Venture & New Process made the 233 transfer case. The tag on the back of the transfer case will tell you which manufacturer it is.

As far as the fix goes, first start by removing the fill plug on the back of the transfer case. If fluid pours out, then the front seal on the transfer case is definitely bad. You will need to drop the transfer case to replace the seal. Also replace the vacuum switch on the transfer case while you have it down.

As far as fluid migration into the vacuum system, that depends on how long the problem was present. It may not be bad. Typically, the 4wd and/or HVAC controls will exhibit problems when fluid gets pulled into them.

 

Thank you very much! That should be an easy fix.
It just came to me now, I forgot that this only happens when the fluid is hot.
Any reason for that?

 

Ok, checked to day and the transfer case was at that point overfilled.
Drained some of it of and confirmed that the fluide level was correct on both the transfer and the transmission, then I took it for a litte drive. When I got back I checked the fluide in the transmission, now it had way to much fluide in it!
Checked the fluide hot both times and in park. Can the fluide leak back in to the transmission also causing that to get overfilled?

I'm going to order the seal and vaccum switch tomorrow, hoping that replacing it won't be to hard. Do I need to drop the transmission or can I get to the bolts to only drop the transfer? Somone have the part numbers for these parts?

 

You can remove just the transfer case.

You checked the transmission fluid with the engine running didn't you? That is just odd...

 

The engine was running, shifted through all the gears and waited for a few seconds in each gear, put the transmission in park and checked the fluid. The last time there was way to much fluid, nearly half the way up on the dip stick.
So it looks like the fluide can leak both ways?!

 

The transfer case is not pressurized... Were there any bubbles in the transmission fluid?

 

Yes, some small egg like bubbles....