After comparing my Lionel 6-11210 Vision Line Challenger to the 1931250 new Vision Line Challenger #3977, I see no reason the articulated sound, un-sync drivers can't be added to the new Challengers.
I don't understand why Lionel chose to manufacture the new Challengers the way they did. It is not the first time they made a Vision Line Challenger.
Sincerely, John Rowlen