what a stupid thing to do

I put my oldest son Chris through college several years back to become a mechanic. That's what he wanted to do. He done well, matter of fact he became one of the youngest ASE certified master tech mechanics at the age of 21. Started working at some of the local dealerships and thought he knew his stuff. He did, but not on the old cars. About a year ago we pulled the center section down in the 73 Dart Sport and I was going to send it out to have the gears changed to the 3:55's that are in there now. My son said that he could do that and I thought .....ok. put it all back together and it ran fine till we was getting ready to go to Cruisin the Coast last year. Just before we left, I was checking out the car and noticed a drip from the pinion seal.
He said he would fix it and we had to replace the yoke at the same time. I told him we needed to go back with a crush sleeve eliminator. He told me that he could mark the nut and put it back where it was and we didn't have to do that. Against my better judgement I thought maybe he knows somethin I don't so I let him do it. I knew better though. We drove the Dart part way down and all the way back. We got going through Nashville on the way home and Tyler told me that the rearend was making a noise. Well you can guess the rest. I felt pretty good the other day and bored so we pulled the car in the garage and pulled the center section out. I could tell the pinion bearing was junk. I took it over to a guy I know that builds dragsters and he took it apart and the carrier bearings were junk too. So I am having the whole thing redone and set up right. I ordered 2 crush sleeve eliminators from Dr. Diff.
Why 2, because he done the same thing with my Duster years ago. That small vibration I have been chasing for years, the center section is the only component I have not checked. I bet some of it is in there. When I get the dart back together, I am going to pull the section out of the Duster and have him tear it down and do it right. You want to think that when you kid tells you that they can do things to let them do it. But I knew better and should have done it right. BIG LESSON LEARNED HERE. If you have to take it down, go back with a crush sleeve eliminator.