Transmission leaking fluid

1988 leaks fluid fairly bad , but only seems to leak when driving. So maily an under pressure type of thing it seems? I havent actually crawled under it yet although I know it is dripping down onto the exhaust pipe ; where the pipe runs side to side in front of the pan area. Any idea's of what I should be looking for? Thanks.

Well the leak is coming from the bell housing so I take it , it must be the fron main seal.Hmmmm How hard is that to replace or is that soemthing I would have to get pressed in or something

I recently had the same problem.... I have a 1993 Aerostar. I took it into the shop because after driving it all day without any problems, I drove it 7 blocks from my house and started to feel slippage.... felt nothing like it before this. About 6 more blocks and it started stalling. Then about a mile more, I noticed smoke coming in. I thought it was from another vehicle so I continued driving. But about another mile proved me wrong.... smoke kept coming in. I pulled over and noticed tranny fluid spilling all over the exhaust pipe (just as you had).... that's where all the smoke was coming from. I checked the fluid level and it was almost dry. I bought another 2 quarts just to get back home. I took the bag streets to get there. Half way home, it didn't want to move anymore. I had to put another quart in and go the extra 3/4 mile home. I kept watching it stream out from where the transmission bolts up to the engine. I was afraid it was the front seal. I didn't dare drive it for 2 days. I sent it into the shop and they told me that the torque converter was overheating and blowing out the front pump. They said it would be $500 - $700 to fix it. I brought the van home with them telling me that local driving shouldn't do too much harm as long as I didn't let it overheat. I talked to a mechanic friend and a guy at Murray's Auto Parts. Both of them (along with 3 other people) told me to just get a Trans cooler. They ranged from $25-$65. We bought one for $40 and put it on. It had a factory one on there (tiny one) that we replaced. This one was 3 times the size. That was 4 days ago. We've driven it everywhere but today was the real test. It was 79 degrees outside and we drove 65 miles on it with ALOT of stop & go and up driveways and down (I deliver the Detroit News). So far so good! I don't know if you have the same problem.... but maybe a trans cooler is all you need too.