Rack and pinion steering is used in many cars. Essentially, the steering wheel turns a round gear -- the pinion -- which in turn moves a straight bar with gear teeth -- the rack -- from side-to-side to turn the wheels. It is a simple arrangement, but it does have some disadvantages.
Because of the simplicity of the system, rack and pinion steering requires fewer parts to function properly. However, this places a greater strain on the individual parts, and the wear can cause leakage, requiring replacement of the rack assembly.
When installed in a four-wheel-drive vehicle, rack and pinion steering can cause problems when driving off-road. While this simple system provides responsive handling on paved roads, the greater force required to turn the wheels on drastically uneven ground can cause it to wear out much more quickly.
Its simpler construction and reduced number of parts help rack and pinion systems provide more road feel than other steering mechanisms. However, this more intimate connection with the road can also transfer more noise and vibration to the driver and passengers.