XVIIINICKK

Hey guys, in new here and I bet I'll be here for a long time now. I'm nowhere near a mechanic, I can change oil and lights, replace belts, one time I replaced an alternator. That's about the depth of my mechanic skills. But I'm learning! My truck hasn't given me any problems since I bought it used about 6 months ago but I was ok the highway one night and my cruise was set, then all of a sudden it's like it kicked into neutral and rev'd way up. I pulled off the to the shoulder and put it in park then back to drive and it drove until I hit 30mph then did the same thing, kicked off and rev'd way up. I did some research and found that it's my overdrive not kicking on. So I did some more digging and found that it may have been a servo retention clip broken off and jammed into something. So I jacked the truck up and followed all the steps to taking it off and inspecting everything. I learned that nothing had broken off, everything looked fine. My fluid was a little brown but no damage in the tranny. So I cleaned everything off, and I mean everything I could touch. Put it all back together correctly, double and triple checked, and tightened everything down. Put about 4 quarts of new fluid in and turned the truck on to cycle through the gears and on my little display is now says "TRANS FAULT" and the overdrive symbol blinks. Continued filling it with fluid and it still does this. Any ideas? Everything I read has my mind running around in circles. Thanks for any help