I have a 2012 Ford F150 XLT truck. While driving it sometimes will lose speed. the dash, which usually shows the gas mileage in digital form goes to just lines(like this ----). My speedometer and other gauges also drop to 0.
No matter how much gas i give it, it won't speed up.But it continues to drive. If i pull over and shut off the truck for a minute or so it usually drives normally again. The check engine light doesnt always come on after this, but when it did i had it checked at an O'reilly's. The man told me it was indicating that my Output shaft speed sensor was faulty. Unfortunately the two mechanics i took asked to change the sensor said they couldn't find it. One even told me that the sensor was on the inside of the transmission and that i would have to change the entire transmission out. Can anyone help me? Has anyone had this problem before?

More info: I don't smell any burning and i've never noticed any leaking when i park my truck.