2001 escape shift problems

I don't know what to look at for sure . I checked both ends of the cable and they look good ( no free play ) but i did notice that at the point where the cable is hooked to the support bracket on the motor there is a oh about 3 inch long round plastic tube that is hooked through the bracket . now the cable goes through this tube but it has a plastic ring around the cable that seems to be sliding in and out of this tube when i move the shift lever . is this part broken or is it suppose to do that ? when i locked vise grips on to stop it from moving the gears worked fine so if anyone has any ideas please tell me . ( automatic trans )