If you catch a torn CV boot quickly, you can usually just repack the joint with grease and replace the boot.

Any water/dirt ingress to the CV boot will require the axle to be replaced, otherwise it will just be a matter of time until the joint starts to make noise and eventually fail.

Get a flashlight and open the 'tear' and have a look at the grease, run your finger on the inside of the boo and feel for grit. If it's a milky colour or you can see dirt/sand in the grease then it will require removal/replacement of axle....halfshaft....whatever you guys call them in the US.

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2005 3.0d Sport - Sapphire Black
Engine : Bluefin Superchip Tune,
Wheels & Sus: Style 168s (10.5s all round), H&R RDA Spacers, Bilstein B12, Eibach 40mm drop, Whiteline RSB
Exterior: Le Mans flares, 4.6is kit F&R
Interior: Dynavin N6, Blackvue DR650 dash cams

My Build Thread: http://www.xoutpost.com/bmw-sav-foru...run-sheet.html