Tranny question

Can anyone tell me what the difference is between a 350 turbo and a 400 turbo transmission? Basically, I have a nice 350 turbo, but someone said I might consider upgrading....I will be mating it to a 350 small block, if that helps. I don't have a rear end picked yet, so I'm open to suggestions there too! I want good off-the-line performance, and good acceleration up to highway speeds. (as opposed to my BMW M635, which is sluggish off the line, but has a sweet spot that's far in excess of the legal speed limit!).

They are completely different animals, other that being automatics and three speeds. How seriuo are you going to build your motor would be my first question. A TH350 is a damn fine tranny and you can build them to take some seriuos ponies with very little work TH400 is a great tranny too, heavier duty than a TH350 basically. You generally see 400's in trucks and mated to big blocks (although I have seen my share bolted to a small block) and 350's are usually in cars and bolted to small blocks. The 400 will rob you of more power than the 350, which will rob you of more power than a stick. I know this is very general info, but I need more info on your car, engine, etc... to say much more. What are you buildin'?, what's it going to do i.e.: daily driver, drag racer, street and strip, road racer. Give me a little more info and I could probably be of more help.

I'm building a 32 Ford Roadster. I have 80% of the parts. The body is fiberglass. Believe it or not, I intend to drive this car quite a bit around town when the weather is decent (maybe 3k miles per year). On a typical day, I'm not even on the highway, but about twice a week, I'm heading across town for some errand. It will not be a drag car, but I want it to be very quick off the line. I want it to get up to highway speeds in a hurry (fast quarter mile).

If I have to drive it 300 miles on the highway at 80 mph, I want it to be up to that task as well...since I will be taking it on a couple cross-state runs to visit people.

Your TH350 should be well up to the task of pullin' a duece roadster around. Probably more than enough. Most people don't know enough about them and have only heard that a TH400 is a "better" trannies. A TH400 is definitly a stronger trans, but overkill in most applications I see them in. For what you are tryin' to do I would consider an O/D trans as an update first. It would give you an extra gear for highway cruisin' and a little better mileage. A TH700r4, or even a TH200 depending on what you do to the motor. But to the original question, I'd stay with the TH350, should be more than enough for any mild small block