So ,maybe your trim knob was moved an the brakes was slightly on ,that will explain why the truck is struggling to move!
The engine runs good ,but the truck isnt rolling freely like the brakes are on ,or something in the running gear is too tight!
The best way to check ,is to turn the radio gear on ,an hand push the truck ,if it rolls freely ,then your good there if it isnt
that ,then your slipper is bad or needs to be tighten!
If that doesn't work then ,your o-way bearing is slipping in the transmission!
Your truck should move quick with out struggle like mine ,here is a vid of mine!