This all started Saturday afternoon.. I was out messing around and it felt like something was holding the car back. So I decided to do a tranny fliud & filter(AOD) change since that is where it felt like, the trans..Anyway did the fluid & filter chang & went out to get the trans up to temp to check fluid. All seemed fine then when I took off from a light, everything was good, shifted into second gear, everything good, but when I shifted into third it felt like I hit the brakes. Car nosed over and slowed down,, shift back to second and everything goes back to normal, until I shift back to third and it does it again. Feels like 2 gears are enagaing at the same time. Any suggestions..