Hi Jeff,
It may be somthing very simple (or not). Make sure you have not knocked off a vacuum line of the several that run from the injection pump up to the 2 valves on the fender well. Maybe while changing oil. These lines (in part) are what control the cold shifting. They do the same thing as a vacuum modulator on a gasoline vehicle, that is, more pressure is applied to the clutch packs in the transmission as more power is produced by the engine. Otherwise you would have hard shifts at low power aand/or slipping at high power.
Since your diesel vacuum does not vary with the throttle position, and since these transmissions shift hard when cold, there are valves to vary the vacuum and these easly damaged lines and rubber "Y" fittings (in part) control that variation. I have the same vehicle as you, best car /engine combo ever.
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