If I had to guess the interface went bad. It's an adapter that allows the head unti to work wth the stock system. It would be mounted behind the stereo. For what it's worth, I wouldn't try to replace it. Just get a whole new speaker system. Sounds better anyway.
That is what a forum is for. We work things out through a process. You may not have the experience or expertise to diagnose an issue but others may have had the same experience and can lend their knowledge. Just because it doesn't work for you doesn't mean it doesn't work.
Hmmm. You got me thinking now. Mine won't start either. We had our house raised and the driveway is now inclined. When I drove into the carport after it was finished I drug the tailpipe, I thought. Maybe I damaged the tank.
Great car. I had a good friend that had a 72 Grande when we were just out of high school. Double dates were a blast with all of the room in those things.
They broke, they fix it. Accept nothing less no matter what each scenario "sounds" like.
The wrong oil could be a culprit as well.
The whole rearend should be replaced. If the bearings are eating themselves that means metal in the axle tubes and raceway so axle bearings and axles would have...