I don’t know how using a flush machine causes a trans to burn up, you fill it with fluid plug it in line with cooler and as old fluid is pumped out it pumps new fluid in at about 45-50psi, even if the machine was pumping it in at 100 psi that’s less than trans line pressure at wot. I gotta go with the other guys and say don’t mess with the trans fluid. It’s filled with detergents it’s not being subject to the by product of combustion there’s a magnet in the pan to collect small debris. Besides that trans fluid doesn’t just go bad, no oil really goes bad it just becomes contaminated. The only time trans fluid should become contaminated is a pump failure bearing failure or a burned up clutch pack, and in any of those cases you’re overhauling anyway