Here's video. It'll start the 3-4 shift around the 0:40 mark.

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'81 MB 300SD, '82 MB 300D Turbo (sold/RIP), '04 Lincoln Town Car Ultimate

Sooner or later every car falls apart, ours does it later!
-German Narrator in a MB Promotion Film about the then brand new W123.

Just a few more smaller items to check (hopefully it's just one of these):

There is a 10 mm nut from the throttle linkage on the firewall to the mechanism close to the valve cover. It loosened on mine and made it feel like it wasn't shifting correctly. I forgot if it felt like 4th gear was amiss or not because this was years ago. Tightened it down and all was well.

More recently, but still a few years ago, the 3/2 valve levers on the black box broke. The cam mechanism on the throttle linkage (black item which contacts the 3/2 valves) would get stuck on one or both of these broken valve levers. Removal or replacement of these would fix the problem (in my case, I removed them).

Hopefully it's nothing major. I only mention these because it's inconsistent symptoms you're experiencing to perhaps it's just a stuck or loose component.

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http://farm8.staticflickr.com/7271/7...144c3fc1dc.jpg

I went through the usual simple-to-check laundry list of transmission items today. The vacuum levels were fine coming from the vacuum pump and at the modulator on the transmission. I think it may need a new VCV, but I'll address that after 4th gear is finally sorted out. The bowden cable needed a slight adjustment, so that was adjusted (the shifts in gears 1-3 are more timely now). The kickdown switch was checked and it was functioning fine. The throttle linkages were inspected and all was well. It still takes its time going into 4th gear though, so those items didn't solve the problem. My MB indy is going to check the valve body next week and see what's going on there.

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'81 MB 300SD, '82 MB 300D Turbo (sold/RIP), '04 Lincoln Town Car Ultimate

Sooner or later every car falls apart, ours does it later!
-German Narrator in a MB Promotion Film about the then brand new W123.

Thought I'd give you an update. After loads of tweaking and adjusting didn't make a difference, the indy came to the conclusion that the transmission needed a rebuild. Once the rebuilder got it apart, they said the fibrous material was gone from the clutch discs. The rebuild is now complete, but as it is with old cars, another issue came up in the process. The driveshaft wouldn't come apart at the splines, so the whole driveshaft had to be removed to get the transmission out. The boot there deteriorated and allowed water and dirt in there which caused it to rust together. No amount of penetrating oil, heat, or banging would loosen it, so a used driveshaft in good condition is going in with a new mount, bearing, and a new Lemforder flex disc I had in my pile o' parts awaiting this moment. An interesting thing the tech found and showed me were some very old marks on the driveshaft where the two halves come together where somebody banged on it with something hard. They weren't fresh marks, so I don't know what that was about, maybe some prior mechanic from decades ago tried to sabotage it long ago, who knows? I should hopefully have the car back late this week or early next week. Looking forward to feeling that proper MB shift.

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'81 MB 300SD, '82 MB 300D Turbo (sold/RIP), '04 Lincoln Town Car Ultimate

Sooner or later every car falls apart, ours does it later!
-German Narrator in a MB Promotion Film about the then brand new W123.

The steel discs in these transmissions are usually good unless subjected to extreme heat. How did those look? The driveshaft has painted marks on there for the alignment of the driveshaft for proper balance and no road vibrations. I'm assuming that the colored red and yellow marks weren't there and the mechanic tried chiseling in the alignment points of the driveshaft. I have to rebuild my 722.4 in my 300D (reverse slips) and I can't wait to feel how mine shifts after I refresh it with a TC and new fibres.

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Only diesels in this driveway.
2005 E320 CDI 243k Black/Black
2008 Chevy 3500HD Duramax 340k
2004 Chevy 2500HD Duramax 220k

Thanks for the update. It is especially frustrating when we spend time worrying on a problem and then we never hear the ultimate resolution.

Glad you are putting that fine vehicle back on the road.