Ford f150 4.6 engine stumble

You have it backwards

What you hear is engine noise from
higher rpm, because your trans is not
upshifting, as a result of your input on
the gas pedal

You need to have a trans or repair shop find out why
you have a delayed or no shift condition

When you get to 4th or 5th gear (overdrive) you also
get torque converter lock-up & things should get quieter

it will be more noticeable at highway speeds if you use D3 as the transmission won't use the 4th and 5th gears. This will result in higher engine revving (watch the tach) and will use more gas. The car may feel like it's accelerating faster at these speeds, but at the same time, engine braking will slow it more when you take your foot off the gas.King Scanner G3 for Toyota Tis and Honda Him

D3 exists if you are going up (or down) a mountain and want the engine to be limited to 1st, 2nd, and 3rd gear rather than "searching" for the best of 3rd, 4th, and 5th frequently (although with the grade logic Honda employs this has never annoyed me). ymmv (your mountains may vary).

D3 Doesn't hurt anything; slightly more fuel consumption as the engine will rev higher, but better to be in "D" for normal driving and let the transmission use its full range of gears

best advice is dont go 40mph in 5th gear... if you are going up a hill at 40mph in 5th gear i have no doubt that it is jerking, your putting too much stress on the engine. shift up to 4th or 3rd you will be fine. 5th gear is an overdrive gear. 55+mph

I am assuming your transmission is a 5speed manual. What is the tachometer reading when you experience this jerking in 5th gear? It sounds like the engine is being lugged. If you are trying to pull a hill or accelerate in 5th gear at less than 40 or 45mph, you need to downshift to a lower gear.

sounds like your fluid is low in trainsmison or your slay cylinder may be needing bleeding good luk

this would be an internal bearing inside the gearbox on the input shaft......you have the shft coming in form the engine, and the input shaft houses 1,2, 3rd and 4th gears.....the 5th gear is located on an intermediate shaft.....and then you have the output shaft...now if you had said all gears i would have said output shaft bearing......and if you had said 5th gear only, then this would be the intermedaite gear.....

but you are only saying 1,2 and 3......why its not happening in fourth is that the gear ratios that the shafts turn in correlation to thre gearing changes as you get to 4, like on a 10 speed bicycle but in 4th it is a 1:1 ratio, so no excessive loads on the shafts are noticeable....

This will require a transmission overhaul......

umm more info would be very helpful is this a gas or deisel truck ? almost sound like a intermitent misfire creating a vibration throught the trans ? when was your last tune up ? maybe your clutch is slipping ? more info would be awesome :)

run the fault codes
check the transmission actuator and vacuum hoses

Check the operation/adjustment of the 5th/Rev gear gate and associated selection levers.
Check 5/R gear lever linkages are operating correctly.

try having the fuel filter changed first and have the timing checked and I don't know how many miles on the truck but check low or uneven cylinder compression pressure remove spark plugs and test the compression with a gauge but before doing all this it could be a weak or faulty ignition system