It can't move forward in "park" because that locks it mechanically. Even if something is wrong with the hydraulic controls, it can't move. This sounds like there's something wrong with the shifter cable. Either an anchor is rusted and flexing or the end of the cable is loose. To verify this, shift to "park", stop the engine, then try to push the vehicle or let it coast downhill. If it moves, it's not shifted all the way into "park".
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Thursday, March 24th, 2016 AT 9:45 AM