The backup light switch is in the transmission itself. It is in the front of the transmission on the right hand side(Looking at the engine from the front)close to the bottom. It has an electrical connector you can disconnect to replace it. By your brief description it sounds like a mis-adjusted or defective neutral safety/backup light switch.
〉 Answered on Nov 25th, 2008 by Amanda J. Pierce, MBA "AJ", Certified Mechanic, Project Coordinator; Primavera Scheduler at VIGOR Alaska Industrial Shipyard & BizzM3ch Solutions