I answered your other post. No need to make multiple posts in different sections on the same topic. Someone will help if they know the answer and have time.

I'm also interested in how to set up physics constraints for wheels and the likes. There are no tutorials or good examples, and the manual's explanation is virtually useless.

Btw, I see you are new. Is this your first project? If so, I'd suggest you try some simpler things first and come back to this. Physics can be rather frustrating, and nearly impossible for beginners to work with. But maybe you're just new to the forums. Dunno. Anyway, I hope someone can help. I need to know the same thing, and I've already got experience with the physics engine. Just no knowledge of constraints and wheels, etc, because there's virtually no info on it, and I've never gotten an answer here.