If the fluid level is that high, you've got other problems. If the torque converter is leaking down and filling the case to the level of the center of the output shaft or higher, there's a problem in the valve body with the converter anti-drainback valve. The fluid level in the case should NEVER get high enough for fluid to leak out of the vent hole in the slip yoke!
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
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