I had a complete rebuild of my 86 PA automatic transmission by Cottmann. Drove it for a while (1,000 miles?) and then let it sit for maybe 6 months. Started driving again and noticed foamy trans fluid. Cottmann said I had let it sit too long and the seals had dried out. They replaced fluid and filter (for a price). At about 3,000 miles it started being slow to engage in the mornings (below about 40 degrees). (Cottmann said it was due to those seals I had destroyed by letting it sit too long.) They suggested I add LubeGuard (which I did). At about 6,000 miles (in 3 years), the fluid is full of metal shavings, the fluid is burned, and it won't shift into 3rd.

Of course, Cottmann suggests a total rebuild is needed and of course, when I had it rebuilt, they didn't offer any extended warranties that I could purchase. Is it normal for a transmission rebuild to go bad that fast? Did letting the car sit for 6 months really destroy the whole thing?

Idn about the older engines, but my 1994 sat for a year, and shifts very smoothly through all of the gears, even at wide open throttle. It sounds to me like you got screwed. Take it to a GM dealership and let them look at it, and let them do the work. Also, if you had a recipt from cottmans, that said anything about a warrenty, take them to small claims court.