Who said the vent tube was for excesss fluid runnoff?. You won't blow a seal on a 700 r4 if your over by about a quart. If you have too much the pressure builds up and if there is too much oil the oil comes out of the vent. We had to run the powerglide low on oil or the pressure would spit the oil out of the vent and we could get black flagged if it was noticed