Just before leaving for vacation for a week, on my drive home from work my '87 245 with manual transmission would not go over 20 mph. Everything was fine until I was about 6 miles from home. As I was making a turn I heard a bang from what sounded like below and to the right. I thought something had hit the side of the car and I even pulled over to see if I had lost a hub cap or if there was any visible exterior damage. Nothing. Then within about 3 miles or so the car lost the ability to drive over 20 miles an hour. The engine seemed fine, I was able to get rpm, etc., but I did start to hear a squeal at higher rpm. The car shifts gears fine as well- reverse, and at lest up to 3rd gear. I managed to limp home and park it in the driveway where it still sits having just returned from away. Before taking it to the local mechanic, I thought I'd try to get a possible diagnosis here. Searching the threads hasn't helped.

I'm pretty sure this car has the M47II, and I know for certain it has the Dana power lock "anti-spin" differential. I've read these rear ends have clutches that wear out. Could that be the problem?

Thanks in advance for any advice.