Symptoms
There is no build-up. Ford's phrasing across every campaign is the same: the transmission "may unexpectedly downshift into first gear, regardless of vehicle speed", and "unexpectedly downshifting into first gear may result in a loss of vehicle control". At motorway speed a forced first-gear downshift locks the driven wheels to engine speed.
Likely cause
Two different causes across the years, which is why they are separate campaigns. For 2011–2013 the campaign names only the six-speed automatic and the fix is a powertrain control module reprogram. For 2014 it is specific: "a loss of signal between the transmission output shaft speed sensor and the powertrain control module". Both remedies are software — the module's response to the condition was what changed, not the hardware.
How should it be checked?
Check the VIN at nhtsa.gov/recalls, then look at *how many* transmission campaigns come back rather than just whether they are closed. On a 2014 truck there are two in sequence, and the second one exists because the first was done wrong: 26V-378, filed 9 June 2026, covers trucks "previously repaired incorrectly under recall number 24V444". Owner letters went out 8 July 2026 and the affected VINs only became searchable on 6 July 2026, so a truck that looked clean earlier in 2026 may not be now. Re-run the check rather than trusting a printout.
How can you check it yourself?
Nothing safe to test for. A fault that arrives without warning cannot be provoked responsibly on a test drive, and should not be. The VIN check is the check — and on a 2014 truck, run it on the day rather than relying on an earlier one.
The question to ask the shop
Which transmission campaigns have been completed on this VIN, and on what dates? For a 2014 truck specifically: was 24V-444 done, and has 26V-378 been done since? Has the transmission ever dropped a gear on its own, and was that reported?