1996 Chrysler Concorde stuck in 2nd gear

Are you sure it's second gear and not first? When your doing above 40, the reason it seems like it's in neutral l is because the first gear is forcing your engine to rev high in order to maintain that speed.

Either way, there are a few reasons why it would do that. All would require you take it in for servicing. Not much you can do about that yourself. Sorry.