I need help. I’ve gotten my transmission rebuilt twice in the same year with a new rebuilt torque converter. When i drove it after a few miles, the transmission started to leak the fluid from the “breather” that it has on top. And that happened both of the times it got rebuilt

 

Overfilled?

 

Yes, most likely overfilled

The Vent(breather) at the top of transmission is there to allow for fluid expansion and contraction that occurs when any fluid is heated and cooled
i.e. 1 gal of fluid at 70degF will be a 1.25gal at 200degF
That's what the Overflow tank in engine bay is for, coolant in the engine, coolant expands when heated, and so does ATF

If you are sure it wasn't overfilled then only other reason is part of the transmission is overheating the fluid, and its foaming or expanding too much
Trans cooler line blocked, or the cooler itself
Bands or clutches slipping way too much
Torque converter generates the most heat when stopped and in gear, because its slipping like it should, and that generates heat