ls1650

hi guys i need some help maybe you can give me some suggestions. some how the inner layer gauge face (speedometer) seems to have some trouble getting up to its normal place (looks like it doesn't move at all). for example when i start the car the rmp goes to 2500 and stays there n the speed meter does not move at all when i press the gas. actually when i press the gas it seems like the car is about to turn off. the voltage gauge does not move at all either. i thought the car wasn't charging and was sucking voltage from somewhere so i replaced a new battery but that didnt solve the problem. i checked my alternator and that works fine. does anyone know what could be faulty? thanks.