Classic/Antique Car Repair: 1955 chevy powerglide transmission, chevy powerglide transmission, air vent

Question
My powerglide burps fluid out the filler tube once in while causing a mess in the garage or driveway.  What can I do?  I have read that you can buy a check valve to install in the lines to keep this from occuring.  Any thoughts on this?

Answer
There is an air vent on the back, top of the Powerglide case that must be plugged by crud.  You may have to lower the transmission to get at it, or possibly you can remove the floorboards over the transmission to see it - I don't recall off hand on a 55 whether or not the opening is over the vent - but there's a good chance it is.  Put the car up on a lift and look for the vent and the outline of the floor opening from below.  You may also be able to get the vent off for cleaning from below.

I don't know of any check valve or where you could put one that would stop this problem. They didn't do this when they were new - so the right fix is to clear out the air vent.

Dick