1976 Mercedes Benz 450sl Transmition issue

The transition will not go into park and has slop in the gears. (Shifter moves some) Could this be a linkage issue or is my transition going out? It does not slip when it is a gear. My 450SL has been stored without running for 3 years; I got it running but when picking it up from putting new tires, it did not go into park. Shifter moves ½ inch (slop) will go into gear and not slip when driving.