I have external tranny cooler plumbed in after the stock radiator cooler. It was probably $40 max. That’s it. My tranny has 200k on it and it does do some funny shit sometimes when trying the shift gears at wot. I’m unsure if that’s due to the higher mileage or the 4.1 gearing plus extra horsepower confusing the trans computer. It hits the rev limiter sometimes before it shifts. It sounds cool as hell but it’s not the fastest way from point A to point B. I’m planning to drop in a lower mileage stock auto trans. I’ll do the valve body upgrade on that trans before I toss it in.