Hello everyone, I am away from home visiting a sick relative and I starting hearing a rattling metal noise under the truck. (93,000 miles) I checked the muffler and all was secure. The noise worsened so I went to a local muffler shop to find the issue. The noise only occurs when the vehicle is in motion. The mechanics said that the noise was from INSIDE the drive shaft. They said that I needed a shim kit and that there was an inch play in the rear differential. I have heard a slight whine from the rear pinion bearing for a while. Does this all make sense? They could not fix it and said the truck was find to drive home - 300 miles. What would the expense be to have this done.