Seems like a funny statement I know but it’s an excellent practice. Sometimes in the automotive trade we have to rely on hunches and experience. In all of the factory training I have taken, this has been constant. From Ford to Mercedes and everything in between this works. There are many cases where we have intermittent problems and the best approach is a new part that we suspect is the cause and try it. This works with the entire car too. If you own a high mileage vehicle that you drive every day, there may be things wearing slowly that you don’t really notice. If you have ever been driving and thought “my car doesn’t seem the same” then you should try a known good unit. Find a friend or a dealership that has a car similar to yours with lower mileage and go for a road test. If this car feels way better than yours, may be time to see an automotive expert. Most driver’s don’t notice when their suspension wears out because it’s normally such a gradual decline in performance, that the operator doesn’t notice and if that is the only car you drive you have nothing to compare to.
When repairing a customer’s car, if the part is not returnable a reputable repair facility will take the time to explain the cost and why they feel it is the most effective next step.