trans fluid blowing out vent

i have an intermittant problem of trans fluid blowing out the venttube of the trans usually after a long ride at 65 or so, local driving doesnt seem to make it do this !?? ant suggestions would be appriciated , thanks

I have the same problem with my 2000 conti with 105,000 miles. Mechanic cleaned out vent and replaced fluid and filter but the problem surface again... only on long rides at highway speeds when air conditioner is on... might be good time to ditch!