Pat,

When functioning, a CV joint acts like a mortar and pestal, with grease being the material "crushed" between the inner and outer races and the ball (bearing).

The CV joint is also dependent upon these three extremely-close-tolerance-componenets working together.

If ANY dirt gets into the the grease, the grease becomes a grinding paste which can very, very quickly wear the joint's close-tolerance surfaces out of tolerance. If you live near the beach, or in the desert, and sand frequently gets kicked up off the road, this grinding paste would be far more damaging than if you lived in the moors.

If you regularly monitor the CV boots and know that they failed just recently, then it is likely that you caught them in time. If you are like most people, have a life, and don't inspect your CV boots every morning, it is possible that this condition has lasted unnoticed for quite a long time and the joints have suffered significantly. Considering that they are split all around, the boot failure was probably the result of fatigue (repeated applications of stress) and did not happen 'cause you caught a tree branch on the way back from church.

So, do you feel lucky?

If you replace the half-shafts, your expense is up-front and you have no more worries. If you just relace the boot(s) you have less of an expense now (although labor is a significant part of this repair) but you have a possibility that the joint is near death and you may have to replace the half-shafts in the near future anyway.

You can use one of those universal split boots and save most of the labor costs--but I'm not a fan of "universal" parts--but it is your money, you can decide.

As mentioned by another poster here, you should first test the joint to determine if it has already failed. Go to a parking lot. Stop the car. Turn the steering wheel full-lock in one direction. Then accelerate into a circle keeping the wheel held at the full lock position. Repeat the procedure with the steering wheel in the full lock position in the other direction. If, during that starting out, you hear a "click-click-click . . ." sound in proportion to the speed, one, or both, of your joints is bad. You can usually tell which side is bad as it is making the clicking noise (or they might both be clicking). If you fail the joint test, you have no choice but to replace the half-axle.

I don't know specifically about Volvos, but CV joints can also be rebuilt. But buying the whole half-axle assembly, which contains the CV joint, is usually more cost effective, because the labor to rebuild a joint is fairly high.

Good luck.

Ken