I have a 2001 Mercury Mountaineer. It won't go above 30 mph and it hits 3000. If you try to go faster, the engine just revs. It doesn't shift into the next gear. If I put it into 2nd gear, I can go 45-50 mph. There are no check engine lights flashing, just the overdrive light flashes, and I am not sure it works anymore. I have no clue what's wrong with it. Any suggestions to keep it out of the shop? The only thing comes to mind is something is messed up with the transmission. Please help!