I recently came across a GM TSB 04-06-01-029J / March 2020 advising not to power flush the fluid from any automatic transmission . It has been found to harm the transmission per GM . GM now advises only to drop the pan and then refill as needed to the proper level . I personally never thought it wise to force fluid under pressure through the inner workings of a transmission as that sends sediment everywhere . Even worse IMO is back flushing a radiator sending sediment into the cooling tubes and heater core . Somethings are meant to flow a certain direction , just ask a guy that had a catheter shoved up his $enis .