First off, Happy New Year to everyone!

So, on my way home from checking out a house all of a sudden the truck started vibrating when getting on the highway. Then it got worse quickly. So I pulled off at the next exit and pulled into a parking lot, the truck shuddering badly any time I pressed the fuel pedal. Had it towed to my local Ford dealer where I am friends with the service advisors and mechanics. I'm thinking torque converter/transmission, but I freely admit I don't know. Here's what I think is pertinent info-

1. I bought it at 84k miles, now 122k. Oil changed every 5k, fuel filters every 10k, coolant every 20k, trans fluid every 20k. No idea what was done first 84k miles before I bought it.

2. Driveshaft rebuilt one year ago. Both fr and rr diff fluids changed a few months ago, along with transfer case fluid.

3. When in park or neutral engine revs perfectly smooth. When placed in gear and fuel is added it starts to shudder, getting worse as revs go up. Does not vary with road speed, only with engine speed and load into transmission.

4. There are no codes at all. All temps were normal. Engine oil and trans fluid level normal.

5. A few months ago when coming home from a trip I suddenly had the same symptoms about 3 miles from home, but not as bad as today. Made it home taking it easy and went to bed. I was exhausted from a long day of driving and when I test drove the truck the next morning to check it out it was smooth as could be, so I thought maybe I imagined it. Symptoms did not reappear until today, a few months and several thousand miles later.

Any ideas?

 

Could it be an injector issue instead of transmission? Had headgaskets done over the summer, studs, and injector o-rings replaced.

 

Does the engine crank smoothly when starting?

 

Thanks for the reply!

Yep. Starts easily (all fluids at operating temp) and idles nicely. When cold and oil temp is below 60 at startup it starts quickly but runs slightly rough for the first 5 seconds or so.

 

Any smoke? Can you see fuel pressure? How confident are you in feeling the difference between a cylinder miss and a transmission shudder?

It could be the transmission, but I think a cylinder miss is more likely. The fuel demands are much higher under load than a free-rev. Dropping fuel pressure will cause missing and will also smoke. An injector simply dropping off will shake but not smoke, I've seen this with loose FICM plugs, but they also miss at idle.

Does it do it in all forward gears? You can manually select 1,2,3. How about reverse?

 

No smoke. How confident am I that I can tell the difference...not sure But I agree that an injector issue is more likely. The reason I originally said transmission was because my friend who was with me at the time said he thought it was either a torque converter or transmission issue. And based on smooth idle and revving in park I at first agreed. But when I thought of the symptoms some more I started thinking transmission just doesn't make sense. A torque converter issue the truck wouldn't move, or would move but would slip a ton and revs would be really high for speed. Transmission was still shifting gears and seemed to be doing its thing, just the shuddering was going on. The more I think about what it felt like the more I think injector.

Which probably means it'll end up being the transmission.

 

I had the same issue. When mine shifted into 5th gear. I added some Archoil into the oil. Well shutter gone. It was 3 injectors starting to stick. I could have swore it felt like the transmission shutter. But it was the engine. Good Luck

 

Thanks, I need it! Will hopefully find out for sure tomorrow...but I'd prefer to replace 8 injectors vs transmission and torque converter

 

Fuel filters, replace both - also blue spring kit.

 

Fuel filters were replaced 2000 miles ago. Blue spring done about a year and a half ago. I guess it's possible the fuel filters are clogged if I got some bad fuel...

 

Soooo...turns out that the problem wasn't transmission or injectors. The double cardan joint went bad. Like...really bad.

Funny thing is before it got towed I thought the joint looked slightly off, but didn't think much of it. When the truck was dropped off and I moved it to park it that must have been the last straw.

 

Thanks for the update.

Yea that looks like it's starting to go.

On the bright side, that looks less costly then a trans or injectors.

.

 

Never could figure out why they don't put a grease zerk in those spots.

 

Ha ha yeah it's probably about time to replace it...

And yes...WAY less than injectors or transmission!

 

Those u-joints actually ARE greasable. They are Moog replacement u-joints that I installed exactly a year ago, and greased every oil change (every 5k). Lasted a whole almost 20k miles. The original u-joints in the double cardan joint lasted over 100k miles, 20k of which were with my lift kit on. I only replaced them because I had to replace the diff side driveshaft u-joint so I figured I'd replace all of them. Not impressed with Moog.