As my post count shows, I'm brand new to these parts, but hopefully that'll change soon. :)
My brother gifted me with a '91 350SD about two and a half years ago. It's had no trouble outside of routine stuff (like shock replacement...they were 10 years old!). Over the last few weeks, though, I've been feeling more and more worried over this weird problem with shifting. Going from second to third, or third to fourth, the transmission clunks and the shift is hard and can be felt inside the cabin.
It's definitely a major change from when I first had the car, and so I took it to Aamco for an external diagnostic. They test-drove the car with me, and I pointed out when it was happening and the tech agreed it was strange but he did not think it was something to be concerned about. He did say, and I checked and do agree, that the transmission fluid is a little old, but not real bad yet (just a faint hint of char to the smell).
So anyway, Aamco wants $200 for a fluid purge, but I can probably do that myself, yet I only want to if that's likely to solve the problem.
That aside, I am particularly concerned because last night, for the first time, I put the gearshifter into reverse and the car did not follow. After restoring the shift lever to park, and then once again shifting into reverse, the transmission followed and performed the shift. I am concerned that if I do not get this repaired soon, this could become much worse.
A colleague also pointed out that if the transmission is electronically controlled, it's possible the system could be out-of-sync as the gears are a little worn, etc. I don't believe this model has that kind of transmission, but I could be wrong.
I've searched your forums here and others on the Web, to no avail. So that's my story so far! If you have any advice, it will be much appreciated. Thanks in advance!