I have just purchased a 1986 Monte Carlo SS that looks to have a built 2004r transmission. I have the build sheet from the previous owner. I have driven the car for almost two weeks with no issues. Friday night on my way home at about 35mph the car down shifted into low gear. I stopped and put car in park and then tried to drive it home. The car will not shift out of first unless i run the rpm up real high to finally get it to shift. Could it be TV cable or the servo ? Please Help !!!!!!