1996 Ford Explorer suspected electronic problem with Transm

Transmission problem
1996 Ford Explorer 6 cyl Four Wheel Drive Automatic

this is a 96 eddie bauer explorer 4x4, aod. Few days ago, speedometer started jumping erratically, and trans would slip out of OD on highway when warmed up. Couple of days later, speedo does not work at all, o/d light on cluster is flashing, transmission shifts erratically & hard whether warmed up or not, and at all speed ranges. Changed fluid & filter, no shavings or debris in pan, fluid smelled old, but not really burnt. I'm suspecting one or more of the electronic components have failed, but not really sure.