1987 300D Trans Problem
 

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.

It shifts from 1st to 2nd then no further or from 2nd it shifts quickly to 3rd then 4th?

Sixto
98 E320s sedan and wagon

It shifts from 1st to 2nd then no further.

The 1st to 2nd shift is normal in feel and timing, after that it there is no further upshift even when revved out to 4k rpm.

"Fluid is down about a pint."
Is this level with warm operating temperature fluid and placed in Park? These transmissions are very finicky about the proper fluid level.

Not up to full operating temperature but yes, warm and in park.

Edit, for clarity.
I topped off the fluid, didn't even take a pint. Made no change in operation.