Drhillier

Hello everyone, I have a 1985 300SD. I am a professional auto mechanic, about 23 years experience. I'm pretty sure I've got the problem figured out but want to ask a couple questions.
So I don't drive this car much, it sits under a car cover for the most part. When I last parked it I unhooked the battery and let it sit for about 6 months. One day I decided to take it out to run some errands. I fired it up, headed down the road and it wouldn't come out of first gear. If I allow it to Rev up close to redline it will shift up to 2nd with a hard shift. I haven't tried to get to 3rd. I'm not real keen on red lining it.
So I swapped the fluid and filter (after the problem began) checked for bad wiring, checked the bowden cable adjustment, tested the vacuum pump, still has same issue.
I believe that the vacuum switching valve with the arm on it is bad. Does that sound right or am I missing something obvious? I believe I have everything I need to do additional testing, but information for the diagnosis is hard to come by.
2nd question... this part is not easy to find. It was only made for a couple years from what I've read, is not rebuildable, and nothing aftermarket is available. Anyone know where I could come up with one?
thanks for any help you could provide. I appreciate it. I have found some used online but who knows if the part is good or not?

chassis

What did you figure out?

What is the shifting mechanism for this transmission? Hydraulic? A cold vehicle sitting for six months that won't easily shift out of first gear sounds like debris is in the hydraulic control circuit. If it has a hydraulic control circuit.

Try warming up the engine in the driveway at idle for 20 minutes. Then drive around the neighborhood at 10mph in first gear for 20 minutes. Then take it out on the road and see if it shifts.

https://en.wikipedia.org/wiki/Merced...c_transmission

I would focus on the hydraulic system.

Drhillier

I gave that a shot. No luck. It shifts but it does it way late and at much to high RPM. I'm gonna put it on my car trailer and tow it to work. We have a fluid exchange machine. I'll see if that changes anything.