I don't know what to tell you guys, I haven't been encouraging him to practise at all - it's DS that's doing it, all on his own. If he says "ac or" I say "Yes honey, that's right Tractor, very good!" then he starts with the "T, T, T... Trac or".
Just tossing out another perspective...
It might be good to remove yourself from the role of evaluating (that's right) and praising (very good!) and emphasize communication simply as a social experience. So that might be something more like "That's a pretty tractor" or "I'd like to take a ride on that tractor", etc. It might help shift him away from feeling like he must master this now.
