2005 Subaru Legacy Owner's Manual - Page 391

Starting and operating Rear viscous limited slip differential (LSD) (if equipped) Power steering " Never start the engine while a tire on one side is jacked up, as the vehicle may move. " If one rear tire is spinning in mud, avoid continued spinning at high speed as this could adversely affect the LSD. " If a different size rear tire is temporarily used (as in an emergency), it will adversely affect the LSD. Always replace it with a regular size tire as soon as possible. The LSD provides optimum distribution of power according to the difference in revolutions between the right and left rear wheels that may be caused by certain driving conditions, thereby improving driving stability on snow-covered, muddy or other slippery roads. Do not hold the steering wheel at the fully locked position left or right for more than five seconds. This may damage the power steering pump. The power steering system operates only when the engine is running. If you lose power steering assist because the engine stops or the system fails to function, you can steer but it will take much more effort. NOTE Right after the engine has been started and before it has warmed up, you may hear a noise coming from areas adjacent to the power steering pump which is located at the right-front area of the engine compartment. This noise is normal. It does not indicate power steering system trouble. 7-36