My '82 300d (natural aspirated) has a 5-speed Gertrag gearbox. It's a greymarket car, noticeable because it doesn't have yellow fog lights, It has a ball hitch with a permanent forged ball, and a 5-speed manual. It also has crank-up windows and a manual (not even a crank) sunroof. A telltale feature is that the serial number plate inside the windshield looks like it's done by hand on a little piece of aluminum, and the number starts with "WB123..." I think. The five-speed lever looks just like a four-speed's. I am told that this is actually an overdrive transmission, but don't know that. It would make sense from the point of view of limiting the number of ring&pinion sets they have to stock.
As an aside, a lot of early-80's US pickups had "4-speed" transmissions that were not the heavy-duty stump-pullers, but were actually the light-duty 3-speed with an overdrive gear built in. On the Mercedes, the manual shows the highest speed attainable is in fourth gear (direct drive) not in fifth (overdrive). This is pretty typical of overdrives. In my old days I had Triumphs, some with Laycock electric OD's, some plain four-speeds. They were quieter in OD, but went faster in fourth.
I've been told that quite a few of these greymarket cars were brought in around then, but don't know how many "quite a few" is. they've probably mostly rotted out by now, wherever they are. I wonder how you'd find them? I also wonder if these weren't more common in Germany, and available as used parts there.
Last year, I came close to buying a motor home built on a Mercedes bus, with 4cyl truck engine, 5-speed trans. Didn't do it in the end, because it was laid out for a couple, not a family of four. This model had never been imported in any number, but the builder told me that he could get any parts for them either new from Mercedes in Germany, or from used-part operations in Europe. I wonder how you'd tap into those.
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