Grinding and clunking/jerk when shifting gears

When I shift from park into drive or reverse it will not engage and grinds until I gas it a little. Then it will clunk/jerk into gear. Will not engage park from reverse. Park will only engage from the drive or neutral position. Once gear is engaged after the grinding then clunk/jerk when I lightly gas it. It shifts fine from gear engaged to neutral and back again. Example from park to drive, grinding, will not engage, I lightly gas it, then clunk/jerk, engages, shift to neutral than back to drive, then to park it works fine. Same for reverse but will not engage park. Also, when I turn corners it seems to make a clunking noise. And when I get up to forty mph and keep it steady it is fine but when I let off the gas it comes out gear. I have to slow down and come to complete stop. I hear grinding until I shift into neutral. I shift back to drive and repeat the whole process I described above. If I keep it under forty mph it does not slip out of drive. Also, the in four wheel drive hi it seems to work fine. But in four wheel drive low same as described above. Thank for your time. Keep up the good work.