Transmission leaking from vent

[merchantmariner]

Hey guys I have a 2005 with 180,000 miles on it currently in the shop for a few things. The mechanic called and said he noticed transmission oil that appeared to be coming out of the vent. He says that to him that is an indication of an overheating transmission.

I know that these things have a pretty robust cooling system so that seems strange to me. I have been driving my rig up to this point and with no issues with the transmission including towing some pretty heavy loads.

Thoughts on what might be causing this and steps I should take next ?

 

[flintknapper]

IF fluid is indeed coming out of the vent...the unit is either overfilled or is getting VERY hot.

ATF does expand significantly when heated...but it would have to get very, very hot (at normal fluid level) to overflow the vent.

First thing I would do is check the fluid level (if the mechanic didn't do that already). IF the level and condition of the ATF look good...then I would check for obstructions in the lines or the trans cooler.

I recently installed a Scangauge to monitor certain engine functions (particularly coolant temp) and in the process noticed that my transmission temps (different trans than yours) were high. I noticed that my trans cooler did not feel warm so I disconnected all the lines to it, the radiator and transmission and blew compressed air through them.

To my amazement....what looks like a shipping plug of some type had gotten wedged in the line going to the trans cooler. The lines to the transmission were fine, the trans cooler at the bottom of the radiator was fine, I had removed and checked the trans cooler, it was fine, but the last thing I checked (the lines going to and from the cooler) proved to have one blocked.

How the plastic part got there I have no idea. How long it had been there....I couldn't say. But once removed... my transmission started running nice and cool.

 

[merchantmariner]

Hey thanks for the reply! The thing that is weird to me is if it is hot enough that it boiled out of the vent so to speak wouldn't I have thrown the AT light on the Dash? I have had no indication of a transmission problem fromy truck except for the leaking fluid.

 

[flintknapper]

Hey thanks for the reply! The thing that is weird to me is if it is hot enough that it boiled out of the vent so to speak wouldn't I have thrown the AT light on the Dash? I have had no indication of a transmission problem fromy truck except for the leaking fluid.

The vent itself might be partially clogged...allowing pressure to build up. It might be worth checking to see if it is fully clear. Many of us extend the breathers for the transmission, T-case and diffs with rubber hose terminating in a filter of your choosing. This insures the vents/breathers do not get obstructed and prevents water from entering from deep water crossings.

You could just wipe the area and then monitor yourself.