Not that I am much help, but do you have a temp guage? It helped tremendously on watching what my tranny was doing vs performance. Sounds like it needs a THUROUGH cleaning!! Not sure how to flush an auto besides a big ol bucket and take the line from the tranny to the cooler and those both to the big bucket. I used a tranny temp/external filter kit that I bought from www.summitracing.com , part number PRM-10677 . Hope this helps a little!!
Jack