I agree with Jim.

My first 240D, a '77 went 280,000 miles before I got rid of it. My second, an '84 now has 533,000 miles. My wife also had a manual transmission 240D for awhile.

None of them ever required any work whatsoever on the transmission. A few clutches have been replaced, and some hydraulic problems had to be sorted out, but the transmissions themselves never required anything but lubricant changes.

I expect the problem you experienced was due to driveshaft problems of some sort.

Good luck,