Hi, my question is I have a 1983 300SD Turbo Diesel, it shifts well 2 times when it reach 45 Miles shifts for the last time, but after that there's no more shifting, however the engine sound that is under too much effort, at 60 Miles per hour it reaches 3000 RPM, I'm afraid to pass the 70 Miles per hour because doesn't sound good. Does these transmissions has an overdrive? or is just me who has that feeling since I just bought the car. Thank You