First of all, the valve body determines your shifts. Not the car. An AOD shift is in an AOD valvebody and the same for a c4. A c4 because of its configuration can more easily be manually shifted. Something to note, some c4's (early ones I think) had a goofy shift pattern and could not be manually shifted so as to benifit you for racing. I can't remember the exact shift sequence. A manual valve body is usually just that, manual upshift and manual downshift or just manual upshift for racing. IE you set your own shift points, kinda like a manual transmission. Also these aftermarket valve bodies are recalibrated with differant "programming" via springs, valves, fluid passages etc. to give you much harder, positive, and non slipping type shifts. In most street driven applications, you could benifit from a simple, cheap, shift improver kit that lets you reprogram your existing valve body for about 50 bucks.