While driving the blazer today I noticed the thing shifting like crap. Doing 45 to 55 mph it kept shifting back and forth a ton. but anyway while under the truck looking at the 4wd parts I noticed fluid all over the place and dripping down. It was all over the place and then the wind blew it all over the bottom of the truck. I tried tracing it and all I can see is that there is a fill/check tube and a vent(looks like a vent tube) right next to it with a little filter cover over it. well that filter cover is soaked and it looks like fluid has been running down the tubes as they are both wet all the way dont to the tranny.

What would cause this to over flow like this? I ran the thru all the gears (2004 blazer automatic 4.3 liter) and check the fluid it is full but is not over full. I can't tell if it's foamy or not. This is my wifes car and I rarely drive it so I have a ton of things to fix. I think I have to start driving this this thing more often.

 

I just found something a little disturbing. I have two posts that may somehow be related. I have been reading through my hanes manual trying to find this stuff out and I may have figured one thing out.

When I said the tranny fluid was at the full mark and not above, that was from checking it a little while ago not from today. so, It may not be right now. How I come up with this is because I was trying to make sure there was no air in the cooling system with the pass side up on a ramp while the veh was running and then I filled the resevoir to the full hot mark after I was done then I took it for a ride with still no heat. When I got back I noticed the leaking from the vent hose next to the fill/check tube for the auto tranny fluid. (this whole situation happend before when I changed the thermostat awhile back trying to get heat).

Now, while reading through this manual I found this: "The presence of engine coolant in the auto transmission fluid indicates that a failure has occured in the internal radiator walls that seperate the coolant from the transmission fluid" I dont know that there is coolant in the tranny fluid but that would explain why all of the sudden I have tranny fluid coming out of the vent tube. Even if it's not that full as to overflow then maybe it would make the tranny fluid foam up that much to make it overflow like that. Also, I figure if this is the case, This would cause the tranny to shift like crap.

Hopefully someone with a little experience with thistype of stuffcan confirm this or shoot it down.

The other post I have has to do with having no heat. Would this cause a no heat situation? May there isn't enough pressure in the heating cooling system to make it work properly with coolant leaking into the tranny through the radiator. Or even have some other affect.

 

What vent tube are you talking about? The one on the transmission? The one on the transfer case? Where? Can you take a picture of the location you are inquiring about?

 

It's the tube just above the oil fill cap. The left one is the dip stick and the one on the right with the saturated foam on the top is the one I am talking about. That foam is saturated and the tube is soaked all the way down to the tranny. There is fluid all over the oil pan and front of the tranny and whole bottom of the truck so it had to leaking alot.

 

Have you followed this down to the other end? Does it indeed connect to the transmission vent or does it go back to the transfer case vent?

 

Both of them as you see them on top are as they are on the tranny. They both run right down to the front of the tranny.

 

How comfortable are you at pulling apart an automatic transmission?

There are a number of causes for a transmission puking fluid out of the vent line.

Could be caused by heat or pump cavity wear. If the pump sticks in the high volume position, it could push fluid out of the bleed orifice and into the vent cavity.

It could also be a plugged or otherwise restricted transmission oil cooler (located in the passenger side radiator tank. You can check this out fairly easily by putting in an add-on transmission oil cooler, completely bypassing the in tank cooler. If the fluid stops coming out of the vent, then you have a restricted cooler. If it does not, then it may be the lines to/from the cooler themselves which you would then have to look for kinks in the lines.

 

I'm not very comfortable with it at all. Never done it before. Is it able to bechecked when changing the fluid and filter or does the tranny need to be removed and torn apart.

 

I would start with inspecting the transmission cooler lines that run from the passenger side of the transmission up to the passenger tank on the radiator. You will be looking for any kinks in the lines.

If that all checks out fine, then the next thing I would do is bypass the stock cooler in the radiator. You can either plumb in a new auxiliary cooler or just use a section of suitable transmission tubing to connect the two hard lines together (as a temporary trouble shooting step ONLY). If you choose to just disconnect the two hard lines and loop them together using a section of suitable tubing, you can drive it around town so long as the temperatures outside are not all that high (winter so this should not be a problem). Obviously, no towing, stop-n-go, or other driving requirements that would result in high transmission heat generation. If this reduces or stops the flow of fluid from the vent tube, then you need to either have the radiator cooler cleaned, radiator replaced, or put in an add-on cooler.

Be aware that add-on coolers may increase the length of time it takes for the transmission fluid to come up to full operating temperature in the winter unless the cooler is covered. Low fluid temperature will result in greater torque converter slippage being commanded by the PCM to put heat into the fluid. Greater torque converter slippage will result in lower MPGs.