Is my ecu bad? on 1995 Toyota Corolla

Sometimes when i'm driving either on the highway/city, my speedometer will start fluctuating and will hesitate to accelerate/jerk. It will snap out of it eventually and return to normal driving. The "O/D off" light will start flashing code 11. What do you think the problem is?

Asked by for the 1995 Toyota Corolla
could be a bad speed sensor
My speed sensor + shift control solenoid were replaced.. no luck :/
could be the instrument cluster