ferraiolo1· 🥇Member Extraordinaire, How-To Author, 🏅TOTM
despite what many think wd-40 (water displacement try #40) isn't a good lubricant. So spraying it on anything to lube it will not last. Spraying inside your CV boot will not to anything. Unless the boot is torn there is grease in there. And its good practice to grease the splines of the shaft to prevent them from sieving fast to your hub. But I don't see that it would cause a squeak.