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What would cause transmission fluid to pour out from the filler tube?

A 1970 Chevy automatic runs fine, except for trans fluis leaking. The fluid is at the correct level, but when running the car, the fluid will rise and pour out from the top of the trans filler tube. This is not a leak around the trans filler tube, as the fluid actually comes out from the top.

I don’t know what’s causing this, but it’s something you want to have transmission expert look at RIGHT AWAY. Don’t delay. There may be a simple, inexpensive cure. This is something you should attend to ASAP.

More than likely you have water in your Auto fluid. It may be from a leaking cooler in the radiator or from being submersed in water. Usually calls for removing the pan for cleaning and flushing the converter well. LEE

Are you checking the transmission fluid level with the engine up to operating temperature, idling, and on level ground? If not, that’s how it should be done.


It might be a tad difficult to get a proper reading with the tranny fluid being pumped out the tranny fluid dipstick/filler tube eh?

With a 38 year old automobile, is it possible that someone put in the wrong tansmission dipstick?

It seems to me that there was some problem back about the 1970 time period with soemthing that caused this transmission overflow problem, but I don’t remember what car was involved and what the solution was. Perhaps someone in an old car club might know the answer.

There is a short vent tube on the top of the case (this is a TH350 or 400) that points downward. Get a stiff pipe cleaner and ream that tube a few times. Pretty sure that will solve your problem.

could just be a simple trashy filter and when it heats up it has no where else to go

mr josh nailed it. Quick easy cheap fix. It has to be able to breathe.

Plugged up vent…


I’m sorry this has nothing to do with this but I’m running out of ideas I have an s10 with a 355 and 350 turbo when I put fluid in the trans it fills the tube up pretty fast but it’s low like low enough to have a hard reverse shift and feel it slipping in drive I can jack the truck up on the dipstick side and it goes in easier but in both cases it will leak out from between the tube and trans and sometimes when driving you can stop and it will leak in the tube and trans do not understand it any help is much appreciated