I just installed a th350 into my 92 Camaro. Every time I search for this leak I always find people with a leak at their radiator. Well, this is not what my problem is. Both fittings that my trans cooler lines adapt into (into the case of transmission). Are leaking. Not the small fittings but the ones that actually go into the case of transmission. I am stumped. I have removed and cleaned everything probably 7-8 times and nothing same results, sometimes worse. All the threads look correct. No stripped threads or anything. What could this be?

 

Some sources say that the cooler adapter fittings are 1/4" NPT (tapered) thread). Others (Jeg's catalog) say its 1/4" NPSM (straight thread).

You might have a mis-match going on between the case threads and the fittings. I tend to believe the threads in the case are NPSM threads. I believe that the straight thread fittings require some kind of seal or sealer.