So this is the 2nd time this happened to me, I took my 2003 mustang and I went on a small road trip about 3 months ago and little after I reached my destination my car started to seize up. The rpms would go up but I wouldn't move (I'm in D btw) so we took it back to my garage, I changed the transmission fluid and it started to work again and honestly it ran better than it did before however this morning it did the same thing and now I don't know what do. I'm kinda attached to this car but I'm trying to convince myself that an overhaul might not be worth it. I'm gonna tinker with it later today and see what's going on. Any advice would be greatly appreciated.