Transmission stop leak will swell the rubber seals in the transmission. Heat kills the rubber. I have used a K&W product called Trans-X in quite a few older transmissions with no negative results. This product was recommended to me 21 years ago and I have since then used it and other products such as the conditioners available from B-G chemicals (which is supplied to shops only I think). We use absolutely nothing but OE specified fluids in any of the overdrive or electronic automatics. We stock three different lubes just for Chrysler products. Any of the many products on the market will claim to do wondrous things as they may well do. If a transmission is shifting erratically, leaking and banging I do not feel that any additive is going to fix it. What you need for your leak only fix is something that will swell your dry hard old seals without destroying everything else. For the authentic farm boy fix, brake fluid added in will swell your seals. The Mobil station here in town does that (cringe, cough, sputter, gasp). Warren Anderson Sedona,AZ