sounds like your transaxles or transmission It could also be a bad wheel bearing - See "Related Questions" below for more
The CV - constant velocity - joints are parts of the axle assembly.Although the CV joints can be rebuilt, I think most people (me included), just purchased new replacement axles when one goes bad.See "Related Questions" below for more about replacing front-wheel drive half-axles.
( yes ) a Ford Windstar is a front wheel drive vehicle and has constant velocity ( CV ) joints
The sound you are hearing could be coming from a starved or defective power steering pump. On front wheel drive cars worn cv joints can make a fuss. For safety sake I would get this looked at asap.
It could be worn struts, worn bushings, worn ball joints or tie rods. Just jack it up and find out which parts are loose.
Lack of lubrication - check ball joints and tie rod ends for wear
lower ball joints need lubed up or probably replaced.
I've had my 2001 Windstar since new and do my own maintenance / repairs - I don't know of any factory installed grease fittings.If there are any, like on the ball joints or outer tie rods, that'll be from having been replaced.
Check your ball joints and your spring hangers
check CV joints
Driving a 4x4 without functioning CV joints is not advisable, as they are essential for transferring power from the transmission to the wheels, especially in a four-wheel-drive system. Without them, you risk damaging other drivetrain components and compromising vehicle handling and safety. It's best to address any issues with the CV joints before driving.
Your u-joints are worn out.
Coming from the drive wheels? Could be worn CV joints