How Many U Joints Should You Replace?
When parts that work together (such as the u joints in a drive line) begin to wear down it is a good idea to change out those parts at the same time to avoid replacing the other joint in the near future.
If one needs replacing...
In most drive line configurations there will be two u joints - one connecting the crank shaft to the drive shaft and one connecting the drive shaft to the rear differential. When one of these is worn or damaged and has not been doing it's job correctly it can put more stress on the other, so starting over with two new u joints will give you the best results. Also if one u joint is showing signs of wear from high mileage or rough use then it stands to reason that the other is not far behind.
While u joints have the potential to last a long time, they do not last forever and some factors can lead to premature failure. So if your driving style or vehicle use fall into those categories and you notice symptoms, then at least checking the u joints is a necessity and replacing them is not a bad idea.
