Th400 ?

[David Dean]

When looking at the tranny from the tail shaft there is a small (approx 1/8th inch) hose exiting the case up by the bell housing in the 2 oclock position. Anyone know what this is for or what will happen if I plug it up. Thanks, Dave

 

[nvrenuf]

It a vent, do NOT plug it.

 

[Ryan B.]

If you would like to see tranny fluid puking out of the dipstick tube, onto the headers creating a fire so you can see "dripping firey lava" off your headers... then go ahead and plug that vent tube.
When that vent gets clogged it will puke out of the dipstick and start a fire, ask me how i know.

If i were you id extend that hose and make a vent for it somewhere up high in the engine compartment. maybe blow through that hose and make sure it is clear also, so that the tranny vent is working proplerly.