That is a automatic transmission, seen several times after sitting a few months having problems shifting, but don't know what would clog up the filter solid, unless wrong or bad oil or a bigger problem.
I have a 44re in my dodge I use for hauling wood, it had no problems last fall and changed oil and adjusted bands about a year ago, but sitting over winter it had problems shifting when I started back up, dropped the pan and just needed to clean the valve body.