Yet another version of SH-AWD was introduced in late 2008 with the fourth generation 2009 Acura TL. The Acura TL implementation of SH-AWD is actually mechanically more similar to the SH-AWD layout in the Acura MDX and RDX in that the rear differential is over driven at a constant 1.7% faster than the front wheels, unlike the Acura RL, which, since its introduction in 2004, added an acceleration device which can over drive the rear wheels up to 5.7% faster than the front wheels.