Ford Super Duty (1999-2016) :: 2001 F250 - Trans Slipping Accompanied By A Sound Like Hitting A Rev Limiter

I have a 2001 F250 SD 4x4 5.4L . I purchased the truck used with about 120,000 miles on it. It runs great despite averaging about 10.8 mpg. Shortly after I got the truck, I noticed what I thought was an intermittent transmission issue when the trans would shift. I would get a "flare" that lasted briefly as if the trans was slipping, but it was accompanied by a sound that I'm not sure how to describe, but it was somewhat like hitting a rev limiter. It only happened when the transmission shifted. The fluid was clean and did not smell burnt. I assumed it was a misfire issue, even though it did not happen often, and seemed to only happen at shift points. I changed all of the plugs and all of the coil packs. It still does the exact same thing. Sometimes it only does it once every couple of days, and other times it may do it 3 or 4 times a day.