Originally Posted by PandaBear
It is a must. My dad's 01 Taurus had a huge amount of ATF burped on the garage floor, because the vent is too short and was stuck. ...
A must for manual transmissions and transaxles, too.
When I had a shop replace the noisy bearings in my Mazda's manual transmission, they used different oil than Mazda specified. I'm not sure the oil difference was the whole reason, but after the repair, the transmission persistently burped oil out the stubby vent pipe on top---even when low on oil. After various unsuccessful attempts to stop the spillage, I stopped it by attaching a vertical section of fuel-line hose nearly up to the hood, with a fuel filter in the middle.