too much ATF causing slipping?

[A20A1]

How does manual trans oil circulate? You might have to add an electric pump just to circulate whats at the bottom of the trans and cool that.

The auto does use a line at the bottom of the radiator.

[Vanilla Sky]

piff, you call that a cooler

[yup, i know you say the same, as you have 2 B&M coolers]

[Raduque]

Manual transmissions don't usually have coolers. And the 3G doesn't have one, and there's no fittings on the trans to add one either. Manual gear oil(and 10w30 in our cars) just sits there and gets stirred around by the gears.

But if I recall correctly, automatics use fluidic pressure to engage the clutches... therefore, auto fluid is already being pumped, and it's easy enough to just re-route that pressure to an external cooler and back into the trans. That is, if the trans is designed to be used with a cooler. =)