HELP: Auto trans just dumped ATF all over my garage!

[Yogawrench]

My brother has a 1991 325i with an auto transmission. The car has 225,000 miles on it, and yesterday he parked the car in my garage after having driven it for a hour at highway speeds. The car idled poorly while in gear, which suggested there was low ATF. The car sat in the garage for at least 4 hours when we noticed a HUGE pool of ATF on the floor.

WTF?

We have not been able to trace any leaks around the ATF sump pan gasket. What would make the transmission take such a dump of ATF?

I have the pan off and have a new filter/gasket kit to replace the filter/o-ring and pan gasket. But before I replace the pan, I need to know what caused the fluid dump. Should I be looking for some kind of clog in a valve or line or other type of gizmo? If so, uh, where would those little bastards be?

I should add that my brother bought the car in 2011 so I know next to nothing about prior service history or problems with the transmission. However, the ATF on the floor was very dark and the sump magnets were covered in a sludge of fine metal shavings.

Guys, any help here would be super appreciated!

[whodwho]

It may have spit the front seal which would suck as the trans would have to come out :(

EDIT: I just re-read it... did you fill it with more fluid before noticing the puddle?

[Yogawrench]

No, I didn't add any ATF before or after the dump.

[Yogawrench]

Isn't there an overflow outlet for when there is too much ATF in the sump?

[TimKninja]

Time for a 5 speed swap.

[whodwho]

There isn't an overflow, it is sealed except the vent by the tailshaft housing.

Curious, did he r3v it up while parked there?

[Yogawrench]

Don't think he r3vd it before parking it. I did find a split in the sump gasket today, near one of the pan bolts.

[whodwho]

Probably no way to know but replace it fill it and run it :)

Just to make sure as some in the past haven't, you do know to check the fluid level with the car running hot and level?

[Yogawrench]

UPDATE:

Last night I cleaned up around the transmission case and cast an eye around for problems. Nothing appeared to be broken, split, cracked or smashed. Changed the filter, installed a new o-ring, put in a new pan gasket and torqued everything tight. Filled the car with 3 liters of ATF, but cant start the car yet. Still waiting on some new parts before I can test for leaks under pressure. Hope to get the car running tomorrow.

[JinormusJ]

Woah nelly

3 liters is overkill. Your gonna be spitting ATF all over the place until it drains to ~1.7 quarts
(axe me how I know)

[Yogawrench]

Woah nelly

3 liters is overkill. Your gonna be spitting ATF all over the place until it drains to ~1.7 quarts
(axe me how I know)

What happened? Where did the excess ATF go? Is there an overflow valve to release excess fluid?

BTW, after replacing the ATF filter and pan gasket, I was able to start the car. No leaks, but the transmission still doesn't shift correctly.
When the transmission is in drive the car idles terribly. In park or in neutral, the car idles fine. What gives?