Awesome guys. Thanks so much for the leads. I will probably try to tackle it this weekend, so it is nice to have a few suggestions of things to check. I will post again if I figure out specifically what was the problem.

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1968 220D, w115, /8, OM615, Automatic transmission.
My 1987 300TD wagon was sold and my 2003 W210 E320 wagon was totaled (sheds tear).