Federal transportation safety regulators are investigating some older Ford F-150s after getting nearly 140 complaints of sudden downshifting on the road.

The National Highway Traffic Safety Administration is probing 2015 to 2017 model years of the pickup. It didn’t indicate how many units the investigation includes.

There have so far been no reports of crashes or injuries, but the unexpected downshifting and accompanying rear wheel lockup obviously increasing the risk of crash.

The downshifting has happened at highway speeds and comes unexpectedly, causing quick deceleration, according to consumer reports of the issue, NHTSA documents say. Some consumers say they’ve also temporarily experienced rear wheel lockup and/or skidding during the downshifts that causes loss of vehicle control.

NHTSA investigators will work to determine the scope and severity of the issue.

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