Check your owner's manual for any scheduled maintenance for your vehicle. Without experiencing the problem, it's hard to say what is causing the noise. I suggest you take your vehicle into a qualified technician that can check your vehicle over to make sure this is not a safety issue. If it is just lube that you need, it's better to do it soon to prevent bigger problems down the road.
〉 Answered on Feb 9th, 2008 by Suzanne Grego, Technician at City of Philadelphia Fleet Management