First, let me tell you since day one I have been learning about this car and I'm constantly being amazed.
1. The transmission failed when backing up with the turbo making boost. I think it was inherent that it would break, given how fast I was going in reverse. Never do that and let the boost kick in and let off, you put undue strain on the transmission and you will break the clutch disks as I did. They are only made out of like a fiber material. When the transmission failed I could only get going once it rolled out at about 2 MPH and then it would be fine. But you have to stop in traffic and that is a bad thing, since you cannot drive that way.
2. Windshield wiper system motor arm broke and needed replacing motor and arm.
3. Window motors failed and needed replacing.
4. Seat motor cables needed replacing to make the seats function.
5. Heat/AC module needed fixing and I soldered the circuits and it worked, have to do it again.
6. AC pump needs replacing since the clutch mechanism on the AC broke a bolt and failed.
7. Small other things like rear window upper valance got soaked and sagged due to my stupidness of not taking 5 feet of snow off of roof in the winter, did not buckle the roof on a permanent basis, but torqued the rear window enough with pressure to let water in on the side. I rubber sealed it and it is fine to date.
8. Radio Becker/Mexico broke for cassette, small spring came off, who listen to tapes, will get an Alpine CD stacker player next.
9. Rear shock came loose and ripped mount on bottom where it bolts to lower swing arm. I MIG welded and fixed it.
10. Besides, tires, valve adjustments, front end alignments, exhaust system components, this is one fine car I plan on keeping for a long time. She needs a little body work, but you have to catch it early enough so it does not go deeper.
Overall... I highly recommend the 1981 SD MBZ over all diesel turbo's. Especially the 1981, since that is the only year I know of with the aluminum hood and rear deck. Mine is going to be converted to a hydrogen fuel cell assist system... I like the idea of getting 60 or more MPG. I might even go diesel electric HHO assist.
The car out handles most cars out there, and for its size that is quite amazing.
Stay away from 300 SDL's and 350 SD and SDL's unless you are a mechanic and replace the piston rods.
If you want to go one step up, and up is what I say... Get a smaller turbo diesel with the 6 cylinder... not the big 350 SD models.