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- NHTSA expanded its probe into 1.27 million Ford F-150 trucks.
- The investigation targets 2015-2017 models with unexpected downshifts and rear-wheel lockup.
- Ford attributes the issue to electrical wear not manufacturing defects from earlier recalls.
WASHINGTON — The National Highway Traffic Safety Administration said on Monday it had expanded a safety-related investigation into 1.27 million Ford F-150 pickup trucks following reports of unexpected downshifts with rear-wheel lockup.
The investigation covers vehicles from the 2015–2017 model years, NHTSA said.
The probe follows a preliminary evaluation the agency opened on March 21 last year, after receiving complaints related to 2015–2017 Ford F-150 pickups equipped with the '6R80' transmission.
The U.S. auto safety regulator said owners had reported that the trucks would abruptly downshift without warning or driver input, causing sudden deceleration and, in some cases, brief rear-wheel lockup or skidding, raising the risk of a crash.
In its response to NHTSA's information request, Ford said the alleged defect in the 2015–2017 F-150s differs from the issue that prompted four safety recalls covering 2011–2014 models.
Ford added that the earlier recalls were caused by manufacturing problems with a part supplied by an outside vendor, which led to loss of signals from a speed sensor.
In the newer vehicles, the automaker said the issue may instead be caused by electrical connections wearing down over time due to heat and vibration, leading to signal loss from a different transmission sensor.
NHTSA's Office of Defects Investigation said preliminary testing also identified an additional risk, showing that intermittent TRS signal loss could cause a vehicle reversing uphill to shift into neutral and roll forward.
The office said it had opened an engineering analysis to conduct further testing and review additional technical data.
