you can replace the boot all you want, it really has no affect, what has happened to it is the boot ripped, and bearings on the inside of the boot have worn down due to not having grease on them. it is better to replace the whole thing in my opinion, but i think they sell bearings, not sure though, i didnt really take time to see if i could just replace them, i just replaced the whole thing, you might want to get both of them replaced, it ran me about $200 and they take the old ones, but thats replacing the axel myself