chepp157

I have the same Shutter in my 06 5.4. did the cheapest fiz first and had fluids transfused to no avail, now over Thanksgiving I will ba having plugs replaced. hoping for the best with this because that shutter really blows. mine happens generally between 40-60

alsatropine

iTrader: (2)

Did you change the gears in the front too or just the rear? Also have u tried throwing her in neutral at that speed to make sure it's not drive line related?

Coachdent2lw

I had front and rear gears installed with 4.88. When I put the truck in neutral at the 60-70 speed it stops shuddering/vibrating under my foot. Lifted front of truck to check IWE's and both are engaging correctly. Both cv axle spin when truck is off while spinning tires and stop when truck is cranked allowing tires to spin freely. Turned truck off and turned tire and cv axles stop spinning.

alsatropine

iTrader: (2)

If it stops shaking when you throw it in netrual, then it's drive line related. Check your u joints for play..

Coachdent2lw

Had u joints checked when drive shaft was checked for balance

Coachdent2lw

To add another note, when I let off the gas totally is when I start to ge the vibration/shudder under my foot around 60-70. If I keep a little pressure on the gas and allow my truck to slow down this way I do not get the shudder/vibration. Looks like I'm probably going to have to take it to the Ford dealership in my area

Coachdent2lw

Went to the dealer today and they told me my torque converter is staying locked???? Told me when he presses the brake it should unlock and it doesn't? But then told me in his opinion it drives good? Is this something prone to the 4.88 gears?

chepp157

I had the infamous shudder it started bettween 40-50mph then started between 40-70. eventually it was throwing a code so I ended up taking it in. It was exactly as we thought it was, there were bad plugs and eventually one of my cylinder's was misfiring (which caused the code). I had all new plugs put in, new coil packs and my truck runs like it is new again! smooth and with way more power!! All in all it wasn't terribly expensive, all things considered.