You can do it, but it’s a bit of a challenge. Disconnect the cooling lines. Put a funnel on the inlet line, and put the outlet into a drain pan. Start the car and pour fresh fluid in at the same rate the old fluid is being pumped out. Once fresh fluid starts coming back out, stop. After you reconnect the lines, you will have to correct the fluid level in the transmission. I’ve never tried this, but I have heard from others who were able to make this work.