1996 Grand Am Transmission Problem

I have a 1996 Grand Am SE 6 cyl with a 6t40e automatic transmission problem. One day it would not shift out of park. I had to use the manual override disc located inside the shifter assembly. My brother has replaced the TCC Solenoid, and it still will not shift out of park on its own, or shift gears while driving. It only seems to be running in third gear. Also, the brake light came on the day taht it would not shift. We've never had any transmission problems with it before, but the speedo stopped working a long time ago. COuld this be related? Anyone have any ideas where to go next?

you may have a VSS (vehicle speed sensor) gone bad, and it's finally shorted to the point where the ECM thinks the car is moving and will not allow the trans to downshift(overrev protection) The park interlock switch may also be bad or out of adjustment. It won't allow you to shift out of park without your foot on the brake.