GM Turbo 350 Transmissions: How to Rebuild and ModifyAlthough not quite the heavy duty performer as its big brother, the Turbo 400, the Turbo 350 transmission is a fine, durable, capable, and when modified, stout performer in its own right. Millions of GM cars and trucks have been built with Turbo 350 automatic transmissions. There always comes a time when the old transmission shows signs of wear. At some point, even the best transmissions need to be rebuilt. In GM Turbo 350 Transmissions: How to