I have a 1987 190D Turbo. It looks like the car has a bad differential. I've never had a failed diff in any car, so I'm a bit amazed. They symptom is a cyclical thrubing noise when the car is coasting. Under power, it's quiet. My first thought was a bad half shaft, and I it seemed louder on the right than the left. So I replaced the right shaft. I also took the time to pull the driveshaft, and replaced the flex disks (which were very worn) and center bearing. No improvement at all. I was contemplating changing the left half shaft, when my wife came home and told me that the car had made a really strange sound...the same thrubbing, only much louder for a few moments. I looked underneath, and discovered that there was a flood of gear oil coating the entire rear half of the car. The diff was almost a quart low (I had topped it off when I replaced the half shaft). The leak seems to be coming from an odd place...behind the rear support, about the middle of the cover. I'd have to remove the diff to see the source. It's definitely not coming from the vent. Sounds about the same to me now.

I can't imagine what I'm going to find inside the diff, and I'm not sure if it even makes sense to fix. Since it's very hard to find parts for a 190DT, what differentials are bolt up swaps? Can I use a diff from a 190E or non-turbo?