Purchased a 99 S70 AWD about a year ago and started noticing odd drive line sounds and car felt like drive line was binding in tight turns left and right. Dealer wanted an arm and leg to remove and replace rear drive line components. Most likely culprit was the Viscous Coupling between the drive shaft and rear differential. (Just a quick note: the AWD system requires all tires to be the same circumference - so all tires must be rotated regularly and changed at the same time. No buying two new tires!)

Long story short, removed the rear drive shaft and guess what, all drive line issues disappeared. Other than a couple more MPG and the lack of drive line noise no other issues to report. I still have the bevel gear flush on my 50K maintenance schedule. Great inexpensive fix for those that don't use the AWD on a regular basis.

Many others with AWD have removed the drive shaft as well.

Good luck - hope this helps.

Oliver