Yes its the light on the overdrive panel that is blinking and also causes hard shifts.
Your transmission is controlled by the TCM, transmission control module. The TCM needs 3 inputs to work correctly. 1) The tachometer signal. That sensor is located on the IP gear housing, forward and to the driver's side of the injector pump. It has a nut fitting, about 1 inch, and 2 wires. Pull the sensor and clean it. If the tach is working, try #3. 2) The FIPL, mounted on the driver's side of the injector pump. This can be adjusted with a multimeter. It has 3 wires. Get instructions. Also, it could have died. 3) The VSS, vehicle speed sensor, located on the rear differential, front side, upper section. It will have a wire. If the speedometer is working well, then look at the FIPL. Ask instructions.
If any one of these 3 items has died or needs adjustment, the transmission, E4OD, will go into limp mode. Don't drive very far this way.