C4 can't take the heat

I have a C4 in a 73 maverick V-8 car. The car sat for about a year. It worked fine for about a week. I tried it the other day--after about 3 miles it began to smoke and stop pulling, I let it cool for about 5 minutes and it pulled and shifted fine. I drained the fluid from the converter and pan. I replaced the filter. Used ford approved fluid. drove it last night worked fine for about 4 miles then stoped pulling. pulled over--waited 5 minutes made it home?????- I have rebuilt a few C4 and C6 transmissions in the 70's but that was a while back--any help-thanks!