This w124 has 105k miles on it and has always been well maintain by "grandpa", the original owner.

Issue;
After stopping to fuel up a couple days ago, the trans no longer up shifts from 2nd to 3rd gear.

I checked the kick down switch, no issue with it.
The bowden cable is not broken.
Fluid is down about a pint.
I don't think a bad modulator would cause a no shift condition, rather a quality of shift condition.

Anyone have any ideas beyond these ? It has always shifted perfect in timing as well as feel, never a hint of an issue.