I have a 2004.5 in my signature. Today it was -45 celcius with windchill here in sask canada. in town truck was FLAWLESS. when i went on highway and accelerated it was good until 92-98 km/hour. i felt a shutter. when i left off fuel pedal it was gone instantly or when i go down hill so i ruled out tires etcc... when i hit towéhaul button to take it out of overdrive it went away as well. and it always happened around 1700-1850 rpms. if i speed up to 110 km or 150 km hour it was gone also.

 

when i accelerate underload it was worse..Like going up hill etc....in towéhaul mode it shifted smooth and accelerated smoothly between first 2 gears but once it went into 3rd gear at about 50 km>hour at 1800 rpm it was vibrating>shuttering again. and out of tow>`haul it didnt do it until 4th gear at 1850 rpms at 92-98 km a hour.

 

I'm not saying it is in all cases, but most of the time, it is your front driveline. There have been thousands of complaint about the vibration from it. Most people experience it between 70 and 72 mph. It is turning when you are going down the road.

 

so you are saying my u joints in front?ill check them. i sure as #$%^ hope it is. i was thinking torque converter/flexplate/4thgear tranny but a u joint makes more sense.

 

another weird thing is if it is driveline/ujoints why when im driving at 95 km/hour and it starts vibrating why does it go away when i instantly hit tow/haul and maintain that same speed? driveline/ujoints should still be driven at the same speed 95 km/hour?

 

You are making a good case for engine miss at 1800 RPM. Try disconnecting a alt lead (stator control) and see if you're getting a RFI disturbance. Only need to run a few miles to see if fixes so you won't run batteries down. You may get a CEL, but that will go away. That is best off the wall thought that can come up with and marry to your issue. Another would be to check electrical connections and grounds. JMHO

 

it vibrates enough that i can feel it in my steering wheel and my window mounted gps vibrates/rattles. can a engine miss at 1800 rpm but not at 2500 rpm? and also if i park in neutral and raise rpm up to 1800 rpm manually with pedal it sounds perfect. so im ruling that out but thanks anyways?

it cant be torque converter could it? it should do it at all gears/shifts? it seems to only do it in 3rd or 4th gear.