Under normal acceleration and @ about 45 mph, -right after the shift into OD; is it at that particular load when she's at her worst. She like thro's a sissy fit and yuh feel like brooming her. Yea, right after OD under normal acceleration. Am I making sense ?? Not ? Then disregard and good luck with it. :wave:

My Guesses
 

Check the U-Joints and center bearing. IF they are bad, you'll need a whole new drive shaft. Replace the drive shaft with one from a 2007 or newer, They have replaceable U-joints.

I have also had a tire that balanced perfectly fine (but unknown to even the tire pros) had bad cords. The truck was taken back to the tire store 4 times for balancing with the same vibration problem as certain speeds. once they move the front tires to the rear, I could still feel the problem, but it move from the steering wheel to the back seat.

My first choice is still the U-Joints.

Instruct the dealer to check Mode 6 data ( cylinder history). If he's clueless, -ask them to stress test the coils. I doubt it's the u joints unless you seriously abuse your vehicle. Everyone I know w/your model year still run their zirk-less original joints. I pulled a car hauler four years back to back. I went thru brakes for awhile, but still run the factory original U-Joints @ 274,000 miles.

I believe you have a low grade misfire. It's not serious enough to cause your engine harm , -via programmed parameters. But it will definitely cheese you off, you'll most likely loose a few hairs in the process.

You can either head to a GOOD dealership and direct them accordingly, - as instructed above. Or, roll the dice and purchase a new set of coils and replace them all yourself.

Good Luck. Common problem, - No Fun.

Ready to hang myself!
 

Try to make this short.
2004 FX4 5.4..
Had tapping in engine. Took to dealer#1. Dealer replaced some lifters, slack adjusters, (one was seized) Cam, timing chain etc.. Got rid of tapping.
Now have engine vibrations at 1100 and 1900 rpms in higher gears.
1100rpms is the worst. While crusing at 1100 rpms I have vibration, can feel in steering wheel. If going up hill in overdrive and at 1100 rpms it gets worse the more lugging on engine. Dealer #2 did comp check on engine and tranny.
All good. This all happened after dealer # 1 did the engine work listed above.
Dealer #2 wants to call Ford to see if they know what it is. If Ford comes up with nothing, they are going to put sensors all around engine etc and drive it to see where vibration is. Does anybody have any idea as to why I have this engine vibration after dealer#1 replaced the parts mentioned?
Did the mechanic#1 something up?
Thanks..
Appreciate any ideas the mechanic should know...

I forgot.
If I leave off throttle when viberating ,the vibration stops instantly..

It might just need new spark plugs and one or more coils.

May I ask why you didn't take it back to dealer #1 that did the work? they would be the most familiar with what was done. But, to answer your question. My first guess would be its a coincidence and as glc stated it probably just needs plugs or a coil.
If the

They replaced plugs and coils..Dealer #1 did check it and said it's ok

Check it again. The coils shorting under load, = low grade misfire.

One of the new coils are bad. Happens all the time..

But would'nt the comp check pick that up?
It runs fine other than what I said.

If they were looking for it. They would have to mode 6 for cylinder history, since it only happens at a certain load.

I know the 1st dealer did mode 6..And probably the 2nd dealer..I feel so lost! I love my truck but can't deal with this crap! Come on! An engine is an engine!..It's like the dealers are trying to figure out a freaking space ship.! Wouldn't you think some body would say.."Hell I know what's causing it" The guy says he has to call Ford.
For what? Isn't he trained to figure this **** out? One minute it runs fine. Mechanic ****s with engine and next it's a freaking horror ride..!!
I'm sorry, but this really pisses me off!

When I take it back to Dealer #2, On Monday, I'm seriously going to tell them "I do not want truck back until it's fixed"! They agreed to give me a loner..Matter of fact, there motto is "We will fix your auto promptly, and done right" Well prove it....

Do you think I should take it back to #1 dealer who did the orignal work and ****ed it up ,and say fix it or else..Maybe a lawyer? Or is that pushing it?

Well iduno. Probably better off to leave it where it's at or whomever you feel that is more familiar with YOUR problems. It's a judgment call. Who are you comfortable with? Have you spoke with the techs yourself?

The techs job isn't always easy, specially with a 3 valve. Having someone else work on it can be good if your receiving really poor service. Other than that, it may work against you.
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So, do they confirm the problem ? They road test to repeat your concern ?