I'm *almost* certain it is not coming from the pan.

Where else can it leak from? It is leaking a bunch.

200,000 miles, fluid changed only once at 145K. No other part of tranny ever touched.

Runs great.

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1986 Black/Gold LG4 Z28
Original Owner, 200,000+ near trouble free miles.
Mostly Stock.

1995 Dark Red Metallic Corvette Coupe Original Owner

 

Does it leak when sitting only, or driving only, or both? Since the fluid level is higher when sitting, the dip stick/fill tube can leak more when sitting than when running. Others require the pump pressure to expose them to fluid like the front pump/TC seal. But, the possibilities are anything with a seal to the outside world: shifter shaft, govenor cover, rear/tailshaft seal, speedometer gear housing, gear shift shaft seal, TCC lockup electrical connector - there's probably more.

The most common is the pan gasket.

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82 Berlinetta, orig V-6 car, now w/86 LG4/TH700R. 2.73 unlimited slip. Cat-back from '91 GTA, Accel HEI SuperCoil. AMSOIL syn lubes bumper-to-bumper. Daily driver, work-in-progress (LB9 w/ZZ3 cam, TBD heads, exhaust, paint, etc.).
57 Bel Air, my 1st car. 0.030 over 396, Weiand Action+, Edelbrock 1901 Q-Jet, Jacobs Omnipack, 1-3/4" headers, TH400 w/TCI Sat Night Special conv & shift kit, 3.08 10-bolt, AMSOIL syn lubes bumper-to-bumper. Best 15.1 @ 5800' Bandimere. Daily driver while Camaro was being put together.

 

Oh, some more info that might be helpful...

It all started in September when the car was parked on ramps for over a month when I installed headers, exhaust, etc. The underside was bone dry until after two weeks sitting and I noticed the ATF all over the pan.
Even now it seems like it will no appear until after it sits a day or two. Does this make any sense?

i also think it is comingfrom within the bell housing.

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1986 Black/Gold LG4 Z28
Original Owner, 200,000+ near trouble free miles.
Mostly Stock.

1995 Dark Red Metallic Corvette Coupe Original Owner

 

Tranny fluid is full of detergents. If you put some new fluid in, it's even worse. The detergent eats away at the seals. After years, tarnish builds up on the seals and plugs any small leaks. When new fluid is added, (ususally after servicing it) the detergent cleans up.

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'82 Firebird, dead stock, 9 bolt disc rear, over 200,000 miles and still going strong, more to come...

 

before my TH200C tranny blew i was leaking everywhere possible. front seal, pan, servo or whatever. i think the torque of my engine was beating the crap out of it. when i opened the pan(after it blew) i saw chunks of medal, biggest chunk was like an an inch, me and my dad were thinking that i tore my 2nd gear apart(because i still had first. i dont think this will help you any. by the way. how much torque can a TH200C take.

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RED82TA5.7L
this car has a bad tranny untill middle of January 2001(im crying inside) soon to be 350 Raptor TH350 from http://www.transmissioncenter.net
1982 Pontiac Trans Am
Cross-Fire Injected 5.7l V8
Eldebrock Headers, 3" Hooker Cat-Back, duel outlet with quad tips.
Mods: 1.6 Proform Roller Rockers, electric fan, Corvette 5.7L computer chip, K&Ns.
Audio: JVC Kameleon CD deck, Jenson 4x6 front, Eclipes 6x9 rear, 2 10" mTx T4000 powered by a mTx 200watt amp.
Black Powder Coated 1990 16x8 Formula Wheels with 245/50/ZR16 Perelli P7000.
For Pictures go to
http://members.theglobe.com/RED82TA57L/mycar/

 

I wouldn't be surprised if you disturbed something while doing the headers. Check the dipstick tube and TV cable (see, I forgot something), both of which are above the pan and would tend to leak while not running when the fluid level is higher. They could also leak over the edge of the TC cover, which could make it appear to be coming from the bellhousing.

 

driveshaft seal, or front pump seal in front of tourqe converter, or converter itself

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1989 firebird formula

Mods: converted from T.B.I. to a carburator 305 to a 350. Flowmater exhaust,hedman shortie hedders,202 heads,350 horse cam,bored.40 over, Edlebrock torker2 intake.

Future mods 400 performer rpm intake (polished) and 600 edlebrock carb, comp roller cam, and way better heads. orpossibly a 383 stroker?

 

I thought I was leaking trannie oil too. But the real truth was it was coming from the power steering. There is one screw or bolt that was lose solved the problem!