I have a 2002 king ranch super crew with around 203,000kms on it, and when ever i get between 50-70km/h the truck hops. I also have a knocking in the rear end at any speed, but the hop is only within that 50-70km range. Also on the highway it can hardly maintain speed and has to pull hard to pick up speed. However in town it will pick up speed like nothing.

 

What does hop mean?
Anything like a grass hopper?
Good luck.

 

Yeah man, are we talking about a shudder, a misfire, a jerk? How recently were your spark plugs, air filter, and fuel filter replaced? Do you have a check engine light on? Happy to help, but we need some details first. I sure as s#!+ hope you don't mean your truck is literally hopping. That would be bad...or cool.

The sound from the rear end could be a drive shaft U joint. They're only about $12 and pretty easy to replace. What kind of sound is it?

 

I'm picturing an F150 literally "Hopping" around, like a frog.

 

Sounds like a misfire based on the description

 

Posters often feel their descriptions are understood as standard by others.
I can tell you that a violent jerk while driving can be the emg brake hardware
has rusted and come apart in the rear drum area.
When that happens the parts cannot get out of the space and begin to jamb the inner drum rotation at different speeds and road vibrations.
Otherwise we all are left to guess this posters issue.
No one gets anywhere much from with guessing.
Good luck.

 

Very true. Specifics make the difference. We haven't heard from him so maybe he fixed it. Does describe a misfire, to which we would suggest looking at the appearance of ignition coils, plugs, air and fuel filters, and O2 sensors (one at a time of course). And ALWAYS inspection before replacement.