Go to the vehicle folder and open the .sfx file (or .aud if Simbin game) with notepad.
Then scroll down untill you find: (Under Ambient usually)
VS_INSIDE_TRACTION_CONTROL
VS_OUTSIDE_TRACTION_CONTROL
Usually this is the rev limit used for cars, you can just remove the last line, for example VS_OUTSIDE_TRACTION_CONTROL=TestCar\Revlimex.wav
And then remove the Revlimex.wav, or remove all the lines after = and replace with Null