I just bought a 2015 F150 Platinum 5.0 6speed with 16,500 miles on it and I have had it for 2 weeks and its transmission is making noises (slipping/grinding/squawking) when going from 40-45 mph when shifting from 5th to 3rd gear. I have taken it into the dealership that I purchased it from and gave the shop manager a ride duplicating the noise with him present. They have reprogrammed the transmission and it's still making the same noise and they do not know how to fix or what's causing the noise. I have noticed several threads regarding the same issue looking for advice or solutions to fix it. Has anyone had the same issues and know how to fixed or the solution or cause?
The video link below is exactly what my transmission is doing.

 

Have the dealer escalate the issue. Don't let them blow you off.