This is not a job for a do-it-yourselfer unless you have a mentor looking over your shoulder to guide you. The boot can be replaced separately, but it is a messy job and you should have a special crimping pliers for the band clamps. The cost of rebuilt half shafts has come down so much, that no professional is going to replace the boot separately. Both jobs require the shaft to be removed from the car, then reinstalled. The additional time required to remove the boot, figure out how to remove the joint, clean the joint, install the new boot, then force in the new grease will cost a lot more than the cost of just installing the entire rebuilt shaft assembly. The mechanic saves you time and money doing it this way, and they know the parts were assembled correctly by the rebuilder.
Here is a guide that will show you how.
If you replace the shaft yourself, there are two places where do-it-yourselfers commonly cause problems. The first is with the large axle nut. That nut must be tightened to a very high and very specific tightness, or "torque". Most importantly, that nut must never be loosened at any time when the vehicle's weight is on the tire. That nut holds the wheel bearing assembly together. If it is loose when weight is placed on it, the bearing will instantly become noisy and make a buzzing noise like the sound of an airplane engine. Where people cause the problem is by setting the tire on the ground to hold the axle from spinning so they can tighten the nut. Instead, just stick a screwdriver into a cooling slot in the brake rotor, then use a click-type torque wrench to tighten the nut to specs.
The second thing to watch for, especially with Nissan products, is to start that axle nut by hand, then spin it on part way by hand. If you use air tools, it is real easy to cross-thread the nut. No warranty will cover that. I have seen coworkers spend hours trying to clean up the threads so the nut will go on. These are a real fine thread on Nissan products, so it is easier to cross-thread the nuts.
Also, a lot of these nuts are "torque-to-yield", meaning they're one-time-use nuts. Once tightened, then loosened, they will not maintain the needed clamping force the next time. When this is the case, the rebuilt shaft will usually come with a new axle nut. Boot kits typically do not come with the new nut. You are supposed to buy that separately.
If you want to pursue replacing the half shaft yourself, the best is to get a copy of the manufacturer's service manual and read through the pages of instructions. That will have line drawings showing where to support the jacked-up car so the control arm can be pried down, how to disconnect the lower ball joint, and will include all the torque specs for the fasteners.
Saturday, April 15th, 2017 AT 9:14 PM