70 coronet original trans rebuilt about 500 hard miles ago-shifts good, doesnt slip at all but when I step on it the trans-shiter jumps into nuetral? I noticed it first a week ago after 2 hard runs through 1st 2nd and into drive, I got on the freeway leaned into it at about 50mph it grabbed for a second and jumped th shifter into nuetral-I tought I just ddnt hve thehiftr all he way into drive from before but it does it everytime I stand on it now, seems to drive fine when no goosin on it but I did very minimal driving because I didnt want to wreck anything else. Any Ideas would be helpful!
