CAR WILL NOT MOVE FORWARD OR BACKWARD BUT RUNS FINE

Question

2007 E-350 sport 143000 miles. Cganged spark plugs, drove 5 miles, stopped and started again about 30 minutes later and car started up fine, but when put into gear (R) the car wouldn't move then put in Drive and still wouldn't move. Put I neutral and would allow me to push it and moved a little but that's all. Had have no previous transmission trouble sumptoms that I know of. I unhooked the battery cables and waited about 30 minutes but it stil would not move. Noticed that the gear shift symbol beside the ODO didn't display . The 'D' or the 'P' or the 'R" would display fr about 2 seconds and then would go off again, whereas they normally display at all times. Help??