The saga continues, another “shudder” issues.

I am the proud owner of a 2010 F-150, 4X4, SuperCrew, Lariat, 157” WB, 5.4L engine connected to a 6 speed, 6R80 transmission with an odometer reading of 178,356 miles.

My issue is a shudder at a moderate speed of 35 – 45 m.p.h. while accelerating. It usually occurs while pulling a hill. If I am hard on the throttle, the shudder does not happen, but if accelerating slowly, picking speed to the dreaded 35-45 m.p.h. zone, the truck shudders. Once I pass 35-45 m.p.h. the shudders stops. While the shudder occurs, there is no fluctuation in the tachometer, and no vibration in the steering wheel. I tried checking the transmission fluid, but to Ford’s infinite wisdom, there is no transmission dip stick. I did find the “so-called” factory dip stick located on the transmission housing, but I can’t take it out. It must have thread lock on it, because it just won’t turn loose. Is the 13/16 nut reverse threads?? I checked drive shaft, carrier bearing, universal “U” joints and all seems to be okay. I do have a set of new spark plugs to replace the existing plugs, but I’m holding off on that challenge. Could a bad plug or misfire cause this shudder? It just seems that if it is a plug, wouldn’t the shudder be present at all speeds?

So far, I changed the left front wheel hub assembly, left front actuator, vacuum actuator solenoid and check valve due to common wear.

Any suggestions??