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Transmission leak because of expansion?

2008 Ford Explorer 4x4. 70,000 miles. Still under warranty. Took a lengthy trip and when we got home I notice a small transmission leak in the front around where the front seal is. No dipstick to check the fluid level so I dont know how much or how long of a leak. Called the Ford dealer and the mechanic told us that sometimes the transmission gets hot and leaks because of expansion! Is this for real?? I’ve never heard this before. I’m figuring bad seal. Have any of you ever heard of this??

“Well, then it shouldn’t be getting that hot. Fix it.”

DING DING DING! (that’s my BS alarm going off) I’ve not heard of it, sounds bogus to me.

Mine sounds like a WW2 submarine dive alarm when I hear stuff like this.
Sounds totally bogus. Insist they fix it.

My BS meter has just pegged at max.

If transmission fluid overheats it can expand and overflow - that normally happens out the dipstick, but you said you don’t have one. But you can’t expect anyone to diagnose leaking fluid based on a phone call.

Go over there and have them put that in writing.

Try calling another dealer and see if you get the same answer!

Absolutely they can leak at high heat, its called venting. Automatics have vents in the pumps, and cases as well as cigroller said, through the dipstick tube. Not BS at all.


So transman why would it be designed that way, the transmission is overfilled from the factory? What are the implications for an owner?

I see this on occasion after a transmission fluid exchange because the slob who did the work over filled the transmission.