I will say automatic transmissions are not my thing - but when I see a vapour trail (found out to be ATF) billowing out the back of my S-Blazer I have enough sense to figure its a transmission problem. I parked it, found the underside of the truck drenched in ATF, and had it towed. . Anyway, it still drove nice and strong to reposition it for the tow-truck operator. Makes me wonder if, or how much, its damaged. I've read a plugged cooler line can cause the trans to pump fluid out the vent. Any ideas?