I don't know if you have or don't have an auxilary transmission cooler added on to your system, but if you don't put one on.

All converters are designed to have slippage in them until they go past their rated stall speed. When converters slip, they make heat, and high stalls can generate a lot of heat.

In my opinion (based on a lot of years in the automatic transmission business), the best cooler available is made by a company called Long Manufacturing. Their coolers are designed like a true radiator(unlike old school tube and fin coolers), and will disipate the most amount of heat. If you can't find it under the Long name, look for it under the B & M name. Don't be shy about the size, and make sure you mount it properly (don't strap it through your rad though). Use it in series with the transmission cooler in the rad, if the one in the rad is in good shape. If the rad cooler is in bad condition, get their largest model and by-pass the rad cooler. I did this on a 71 Duster I owned years back, and never had any heating problems from either the transmission or engine.

Graham