What you will need to do is this. Disconnect the transmission cooling lines (steel lines) from the cooler assembly. Next, using a pump, you will need a cleaner and some fresh fluid to flush the cooler.
It really isn't hard to do, but the pump may be the issue. I believe you can get the cleaner at most parts stores. Once the flush is complete, blow compressed air through an open cooler to blow out any additional dirt and dirty fluid.
If you look below, I attached the directions. Take a look through them and let me know if you have questions or if there is something I can do to help.
See pic below
Monday, August 30th, 2021 AT 7:58 PM