Sometime in the last 3 months and 2500 miles, the dust boot for the fr rgt wheel tore open completely. I still want to keep this car for several more years as it only is up to 100K and all else appears fine. Replace just the boot or the whole half axle assembly?
Considering the difference in cost, I would replace the whole thing now. It would be worth it to me just to avoid the worry, not to mention kicking myself if it goes out in two weeks after doing just the boot.
Back more than a few years ago, I would have gone the other way.
The boot tore open, a good deal of grease has now run out, and a good bit of dirt has moved in. You could replace the boot and grease, but the dirt will remain, the damage is done, and the CV joint will make noise within the next 3 months.
Or just replace the half-shaft now, and not worry about it.
The reason many mechanics replace the whole axle is because the time and labor necessary to remove the axle, remove and disassemble the CV joint, clean it, inspect it, replace the boot, repack the CV joint, reinstall the CV joint on the axle, and replace the axle assembly costs more than just replacing the axle.
Replace the axle and forget about it for another 100K. Then be prepared to replace the other side soon, because if the boot on one side is worn through, the other side won’t be far behind.
I’d have both sides replaced now. Then it’s done.
And have transmission fluid replaced at the same time. This is extremely important with this vehicle.