I have a 2005 F150 XL 4.6L 2WD automatic and this problem just started a couple days ago. I would drive at a normal speed and normal accelaration and before my truck shifts to third gear it would rev up even though Im accelerating at a reasonable rate and not racing it around. It even feels like its not shifting at all or if it does shift up to third it would downshift randomly. It would try to shift up but still at 2nd gear. I cant tell what RPM its going up to because XL has no tach but it sounds like 6-8 RPM at 50 mph before it even attempts to shift. I have a 1000 miles left on warranty and cant get it in 'till next Tues. Please help so that I dont hand the keys over to the dealer without any idea as to what the problem might be.

Another problem, a small one I think, is on cold days it seems like when I accelerate engine makes a whining noise like a supercharger would make but not as loud. Any ideas? Thank You.

 

Sounds like it is slipping. My jeep did that for a little bit, then I changed fluid, and it stopped.

 

Change the filter and fluid