Transmission Gear Indicator Problems of Chevrolet Cavalier

While driving at highway speeds or for extended periods of time four-speed overdrive transmission will automatically shift down to a lower gear, and "ets off" and "check engine" lights come on simultaneously. Vehicle remains in low gears until lights go off or until vehicle cools down. Also , that when this problem occurs vehicle jerks and vibrates as if the abs is kicking in at speeds in excess of 40 mph. Please provide any additional information/attachments.

See all problems of the 1996 Chevrolet Cavalier 🔎.