A TSB is not a mandatory repair that the dealer has to make. What it is is exactly what it's title says " Technical Service Bulletin" They are instructions or information to help the dealer isolate or repair a problem which evidently occurs often enough in the subject vehicles. Just because a TSB exhists for your vehicle doesn't mean that your vehicle has the problem described in the bulletin. A TSB may state that a rough idle may be caused by a particular hose that may cause an air leak on some vehicles that were manufactured wit the hose too close to a sharp part. Not all vehicles have the damaged hole, nor are they likely to have them cut. When you bring your vehicle in with a complaint about rough idling, the TSB will give insite to the dealer of a possible cause and the recommended repair procedure. A "Call Back" is a required repair that must be made on the affected vehicles.
Many steel driveshafts work perfectly fine. Mine for one. Although there is a TSB on high speed vibration caused by a possibly unbalanced driveshaft, they are not required to replace mine since Ido not have the problem. If on the other hand the steel driveshafts were failing and causing accidents, there would be a "call back" and all affected vehicles would have a repair or replace done on the steel driveshaft.
