Originally Posted by lash
That seems like a likely scenario to me, but in that case wouldn't you then end up with coolant in your trans fluid also?
You would think so, since the coolant will remain pressurized on a hot shut-down, while the trans fluid pressure should drop to zero. That'* why I suggested above that he check out the trans fluid for emulsification. Probably best to drop the pan, as that is where any coolant would end up.
But maybe it is possible for the trans fluid to go just one way - into the coolant. Consider a crack in the trans fluid cooling coil that can just seep a little into the coolant when the line pressure of the trans is up to open it a bit. When the line pressure drops, the crack closes. That could explain how trans fluid could get into the coolant but not the other way around.
Just thinkin' out loud.