PONTIAC G6 INSTRUMENT CLUSTER GAUGES SPEEDOMETER NOT WORKING

I Have The Car Listed Above Gtp. I Replaced The Transmission With One From A Monte Carlo. My Speedometer Won't Read Over 25 Mph. It...

My Speedometer Says I Am Going Faster Than I Actually Am.

Car Starts Runs, Shifts And Everything's Fine. However, The Speedometer Saying Error And The Needle Doesn't Work, It Moves When I...