I have a 1994 Plymouth Sundance with a 5 speed. Sometimes the car will not shift out of gear, but the gear shift will go up and down (but only in line...example, if I'm in 2nd, it won't shift out of 2nd, but the gear shift will go between 1 and 2). If I slam the gear shift hard into the gear it's stuck, and then gently shift it out, it will then go back to normal (for the most part, not always, at least without fenagling). What's causing this problem?