My Jimmy has a rebuilt 700R4. It was rebuilt about 8 months before I bought. No wanting another tranny failure while I own it, I installed an external cooler.

http://thumb13.webshots.net/t/63/663/7/14/9/2284714090054440533IZMuyh_th.jpg (http://good-times.webshots.com/photo/2284714090054440533IZMuyh)

Installation was easy. I also installed the lines reversed because GM changed the hose connections. After verifying the return line, I redid the lines for maximum cooling.