I have a 2000 Concorde with the 2.7 DOHC. The spedometer wont move and the car goes through park, neutral, and into drive where it is stuck in 2nd or 3rd gear. 2 months ago the ECM whent out and it killed my alternator and battery and all 3 where replaced. Can anyone tell me a solutionf to the new problem or tell me if these 2 problems are related? Thank you.

You need to replace the speed sensors that screw into the driver's side of the transmission. Probably only need one of them, but they are cheap (@30 at RockAuto.com) so I always replace both of them. Dead give away is when the speedo doesn't work along with the trans. stuck in second.
Good Luck! This is a pretty easy repair.

Needs speed sensors.The 1998 and up transmissions do not go out.They sit on the shelf at most auto salvage yards.