If you have the DPO transmission the chances are you have a broken band. Gearbox removal and strip required. If you have the older box it will also need to come out. DPO vehicles may be driven after disconnecting the trans computer after you have moved the selector to 'N' this should give you third and reverse. Reselecting 'P' wil not let you move back to drive due to shift interlock. The gearbox computer is next to battery.
mags, November 2009