I don't think it would be bad on the street. There are guys on tech who are running them and all the ones I've read about say that they would never have a synchronized box again after going that route. Basically what it would be like is similar to a motorcycle transmission which uses dog engagement. So in a car, that would be the only tradeoff as far as I can tell, it would no longer be silky smooth and quiet like with synchros, but a positive audible "CLUNK" when you engage gears.
Bookmarks