I've seen a rack and pinion setup on the axle for semi trucks with an I-beam front axle, really big. That was at a trade show about two years ago, haven't seen any on the road (haven't been looking either) and haven't heard anything good or bad. Didn't see it or anything like it at the same show this year either.
I also have the same concerns as Steve, and don't think it's a good idea with what's out there now, possibly never.
When there is a factory vehicle with the appropriate sized rack and pinion on an I-beam axle then I'd say that's probably a good start, but for now trying to design and make something else work may not be the best of ideas.
Grigg
