Hello. Not always but sometimes when driving down the freeway I will notice my RPM's a bit high and all I need to do is lift the Shift Lever and take the weight off it and the Trans will shift into overdrive. I have my Trans in a shop being rebuilt and they say my 4th gear is toast and they are asking me if I'm downshifting to do engine braking which I'm not. The only thing I can think of is this glitch. The Indicator is in Drive the whole time. Shifting into P, R,N,and Drive are all normal. I haven't tried to shift into 1 in a decade or two so I'm not sure if I can or cannot. I see there is a cable adjustment so I'm assuming my cable might of stretched a bit. What else would cause this ?