Show me actual data that our old loose tolerance transmissions do better with super expensive fluids. I never said trans fluid hasn't changed since 1965. Its come leaps and bounds. Even cheap modern fluid is way better than anything they had back then. But again it's moot, modern fluids are designed for boxes with modern tolerances and materials. I bet you I could take two 904s freshly built, one filled with dex/merc and one with atf +4 and install them in two cars. I'd let you test drive and I'd guarantee you wouldn't be able to tell me which is which.
