5.4 Triton V8, ~143K miles, problem just appeared this year. Seemed like I would occasionally hit a 'rumble strip' while in OD (~50 to 65 mph) and letting off and then getting back on the gas slowly. Took it to a trans shop for diagnosis which didn't find anything wrong. They changed the oil and filter and added what the shop referred to as 'lubricant modifier'. Made the same 180 mile round trip that had produced this symptom previously and it didn't do it so I thought the problem was fixed. Today I drove it and the judder was back, not as bad and now it seems to be happening when it is just dropping out of OD. Doesn't feel like a misfire issue as the engine pulls ok under load in any gear, only happens in the OD shift range around 1500 to 1600 rpm. Actually watched a Youtube video with a mechanic talking about this same kind of problem with F150's and advising guys that something called 'Instant Judder Fix' could be the cure. Can't believe that a lubricant is actually going to fix something that took 143K miles to develop.

Does anyone know what is actually causing this? Could it be the torque converter? Something in the transmission that's failing? Am I looking at a rebuild or replacement?

 

That is classic low grade misfire. Spark plugs and/or coils.

 

I agree. I've fixed dozens of vehicles with these exact symptoms. Plugs and ignition coils have always fixed it.

 

I'm not inclined to randomly replace things in hopes of eliminating a problem so I took the truck to Ford yesterday morning for diagnosis. Needless to say they have yet to pin point what is causing this even after driving the truck with the analyzer. They still have it this morning and will try again today, hopefully finding the weakness that is causing this. Diagnosis of something that only happens once and a while can be a real bear but the last time a COP went out I was 90 miles away from home and driving back on 7 cylinders was not enjoyable. More to come.

 

Perhaps Mark could educate me a little more about the workings of this transmission. I assume there is some signal/signals that are used to tell the torque converter to drop out of lockup. Is it possible one of these could be faulty/weak/intermittent to the point of causing a brief but rapid fire pick up and release of a lockup release solenoid in the transmission?

 

It uses pedal position, engine speed, trans gear, vehicle speed, trans temp, engine temp, converter slip, and probably a few others I can't come up with at the moment.

I have never seen torque converter shudder caused by an electronic problem. I can't say it couldn't happen, but it isn't likely. I've seen low grade misfire cause this many, many times.

 

Well, had Ford running diagnostics which took them awhile since the problem(s) weren't easily discernible. I've had both complete COP failure (obvious) and misfire under load (also pretty easy to detect). This time ignition breakdown seemed to be occurring under very light to no-load conditions. They finally determined weak COP's at 2, 5, and 8 (need to dig out my records, if memory serves those cylinders have been involved in past adventures). Bottom line, offending COP's and plugs replaced but I haven't driven the truck enough yet to finally call it a success, certainly hope so!

Thanks to all for sharing your knowledge.