New tests are in on the redesign of the most popular vehicle in the country... And there might be cause for concern for some owners.

FOX News Radio's Chris Hoenig reports:

Ford swapped traditional steel frames for lighter, high-strength aluminum in the 2015 F-150, the first major pick-up to do so...

(Commercial) "Up to 700 pounds lighter, so it can haul more than any half-ton pickup on the planet."

But crash test ratings produced mixed results...

The four-door Super Crew version earned the IIHS's top rating, but regular and Super Cab versions missed the mark.

The difference - the Super Crew has steel energy deflectors in its front end - the lower scoring models didn't. Ford will add those to all F-150s starting with the 2016 model year.

The F-series has been the nation's best-selling vehicle for three decades.

Chris Hoenig, FOX News Radio.