enzso

Just bought a K13 Micra auto with 80k on the odo. The gearbox is smooth and shifts well but I've noticed when it shifts from 3rd to 4th at around 40mph I get that familiar rumble when the revs are too low for the gear. The noise stays until I'm up around 45-50mph. It makes it tricky in 40mph zones as I'm having to use the overdrive switch to shift the car back to 3rd. Any tips?