Ok -- I got under the car this evening and looked at both flex discs; they're both intact. I didn't even see any cracks in either one.

I verified the vacuum line is connected to the transmission.

I started up the car with the rear wheels up on jackstands. When I put it in reverse, the wheels turn in reverse. When I put it in drive, the wheels turn forward. But nothing when the wheels are on the ground and under load.

Driveshaft looks intact and normal.

I dropped the pan and looked at the fluid (which only has about 5 miles on it) and compared the filter I installed to the one I took off the car.

Filters are identical.

The fluid has metal particles and again looks burned -- has black swirls throughout -- but does not smell bad.

After replacing the filter and refilling with ATF, still the car will not go anywhere.

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Lots of diesel W126s in the past
Current: 1991 Toyota 4Runner with an OM603