The National Highway Traffic Safety Administration (NHTSA) has widened a safety-related inquiry to encompass approximately 1.27 million Ford F-150 pickup trucks from the 2015 through 2017 model years after receiving reports of abrupt downshifts accompanied by instances of rear-wheel lockup.
According to NHTSA, the expanded probe follows a preliminary evaluation the agency opened on March 21 of last year. That earlier review was prompted by complaints specifically involving 2015-2017 Ford F-150s equipped with the 6R80 transmission.
Owners reported that their trucks would unexpectedly downshift without warning or driver input, producing sudden deceleration and, in some cases, short episodes of rear-wheel lockup or skidding. Those behaviors, NHTSA said, increase the chance of a crash.
In its response to NHTSA's information request, Ford told regulators that the apparent defect in the 2015-2017 F-150s is different from the problem that led to four safety recalls covering 2011-2014 models. Ford said the earlier recalls resulted from a manufacturing issue with a component provided by an outside vendor that caused loss of signals from a speed sensor.
For the 2015-2017 vehicles under investigation, the automaker indicated the reported faults may stem from electrical connections degrading over time due to heat and vibration, producing signal loss from a different transmission sensor.
NHTSA's Office of Defects Investigation (ODI) also reported findings from preliminary testing that highlighted an additional safety concern. ODI said intermittent loss of the TRS signal could, under certain conditions, cause a vehicle that is reversing uphill to shift into neutral and roll forward.
In light of those findings, ODI has opened an engineering analysis to carry out additional testing and to review further technical data related to the transmissions and associated sensors.
This expanded regulatory review leaves open questions about the root cause and prevalence of the fault in the specified model years while authorities and the manufacturer continue technical evaluation.