Ford 4F27E transmission flares from 2nd to 3rd

[pishta]

This is on a 2008 Focus S (roll up windows, manual door locks, base everything except 4AT option) with the 4 speed automatic that I previously owned and is now back with me. It’s got about 119k miles.
Car sat for about 10 months while it was given to a family member as they had an unexpected health problem.

Prior to giving it to them, I had dropped the trans pan and change the filter and replaced the fluid with Valvoline Maxlife ATF. That was about 7k miles ago. I noticed that during cold starts, the first shift event going from 2nd to 3rd results in a flare. It shifts fine from 1-2 and from 3 to 4. Basically, it will attempt to shift from 2-3 but the RPMs go up about 500-1000 revs for a maybe a second or two and then it shifts. After this is done, all subsequent shifts from 2-3 and other gears are all normal.

I did cycle out some more ATF via the trans cooler line - 8 quarts total (2 Maxlife ATF + 6 Valvoline Dex6/Mercon LV blue bottle). Same problem persists. Fluid is clean and pink and at the correct level.

Any recommendations on what could be causing this issue? CEL light isn’t illuminated on the dash.

2-3 shift is the band releasing and the fluid filling the back side of the piston bore as an accumulator. There is a wear point in this trans in the case where the piston pin goes through a precision bore in the aluminum case. This should have been designed with a bushing here but the AL case wears out and leaks the accumulator fluid past here as this is the same piston that controls the the 2-3 clutch engagement timing. It ends up drawing out the clutch engagement that wears out the clutches. There is a $75 kit that you can buy that allows you to pull pan and side cover, drill out this bore, ream it and hammer in a precision bushing that stops this leaking and the clutches/steels can be replaced by pulling the end cover off the trans and replacing the frictions and the 2 oil seal rings in the cover itself. It can be done with trans in car up on jackstands. End cover is held on by T-40 torx (or hex bolts if your lucky) and is very close to frame so you may need to unbolt motor mount under battery to get trans down about and inch to access the fasteners.