I have a 2003 Dodge Neon SXT. The car drives great for about 20 minutes, seems like once it is heated up the transmission just stops working. The car is basically in neutral. No gears work. I let it sit for 30 minutes and it starts working again but not for long. If I let it sit over night it works for 20 minutes and repeats the same process. Fluid is good and no check engine light or any warning lights are on. I have changed the filter and fluid twice with no improvement. Any help would be appreciated? Thanks!