Hi. I have been having problems with the front axle not always wanting to lock, especially when it is really cold out on my '98 blazer. So I took out the actuator that locks the front axle this morning, to find that it had quite a bit of ATF in it. I cleaned it out, rinsed it with some carb cleaner, and it seems to be working pretty well now. But it isn't very cold today.

I am thinking it didn't want to shift when it was really cold because the ATF thickened, and couldn't move through the vacuum line.

My question is, where is this ATF coming from, and how do I stop it?

Just a little history about the vehicle. Aside from it having just about all of the standard issue blazer problems, I lose ATF from the transmision at a very slow rate, but never find any on the ground. A mechanic friend of mine suggested that the seal between the transmission and the transfer case might be bad, and the losy fluid could be going into the transfer case, and maybe out the vent as it gets full. Does this sound reasonable? Would an over-full transfer case cause the ATF to flow through the vacuum hose and out into the axle actuator?
Thanks for the help,
Jeff

 

The ATF is coming from the transmission via a leaking input seal on the transfer case, through a leaking 4wd vacuum switch (also on the transfer case). If you were to pull the fill plug on the back of the transfer case, you would find that the transfer case is over full by a few quarts. This is a somewhat common problem.

Hopefully the ATF has not worked its way into the vacuum powered HVAC components as that can be a real pain to get cleaned out!

 

Thanks, the leaky switch is kind of what I thought after searching some other threads, so i will go get a new one in the morning. As far as the HVAC, I haven't had any problems with it yet. I will also drain the excess fluid from the transfer case.
How difficult is it to get at the vacuum switch? To me it looks like it will be an easy fix "IF" I don't have to dissasemble half the vehicle to get at it.

 

I've just been through your entire ordeal with my '98 Jimmy. It's pretty easy to get to the vacuum switch. You'll need a 7/8" wrench to remove it. It's on the top of the transfer case and you can access it without removing the transfer case from the vehicle.

I went through and did the complete repair. I removed the transfer case and replaced the failed seal. I also cleaned all the ATF out of the vacuum lines by flushing them with Simple Green and then blowing them out with compressed air. I removed the HVAC controls and rebuilt the vent switch with parts from three various switches I had on hand. I also replaced the 4WD actuator under the battery. Now the HVAC system works perfectly and everything is free of excess ATF.