the higher the number in the ratio, the more spins of the tail shaft is needed per revolution of the wheel. In this case, a 3.08 will need 3.08 rotations of the tailshaft, for every 1 rotation of the wheel, and a 3.89 will need 3.89 rotations of the tailshaft for every 1 rotation of the wheel. So as the ratio number gets higher, the more rotations needed to propel the car along at the same speed. The more rotations you have, the faster it will accellerate (to a point). The more rotations (the higher the ratio number) the higher revs at a select speed. In an Auto 6cyl VL, in overdrive, at 100kph, and 3.45:1 ratio diff will see you sit on about 2000 revs. The same car with 3.89:1 ratio diff will see you sit on higher revs, about 2200. Hope this clears this up.