I am going through this right now with our 85 TD. My wife drives the car daily. While away, I had a mechanic check it out and he found the center bearing coming apart. I had him replace it. I asked for pics of the parts on the entire shaft and got nothing. The part was installed and it was ok for a couple months. I am now visiting, and the car had a terrible banging sound. I could not believe my wife was driving it.
I took it apart the next day and found the new center bearing destroyed and both flex discs badly worn, if not nearly trashed.
I ordered new discs, center bearing and bushings. There was no listing for the u joint. I guess I am going to have to order that by dimensions. (??)

I have the driveshaft back together with a notchy u-joint. We will see how well it drives tomorrow.

Question here is, where to get a new u-joint?

Fingers crossed the center bearing doesn't fail again until I get that joint replaced. My wife loves this car and is chomping at the bit to drive it again.

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85 300D 3 pedal. Current project.
83 300TD (need rear wiper assembly dead or alive)
84 300SD Daily driver
85 300TD almost 400k miles and driven daily.
98 E300D *sold
86 300SDL *sold and made flawless 10 hour journey to new home.