I recently replaced the radio in my mother-in-.

I recently replaced the radio in my mother-in-law's car with anothe OEM radio. After I finished and she drove it, she reported that the speedometer is erratic. Any ideas of what I may have done? I did remove the dash panels to remove the radio but put back everything in order, including the conections.
Any help with this would be appreciated. And by the way.I really like my mother-in-law. She's a nice 82 year old Texas lady!