Thought I'd post this up incase I can help someone else. I have a 2004 FX4 Supercrew with 82,000 miles. About a week and a half ago, I really started having a bad vibration when my truck was in overdrive (on the interstate about 50 - 60 mph). Once the truck got in OD, if I sped up without making the truck downshift to 3rd, my truck would start shaking and I thought it was my transmission. Now, this was the only time I felt that I had a problem with my transmission. My transmission shifted fine; if I drove with OD off, I had no problems at all.

But then I did some research on this site. I found a few posts where members had mentioned a 'low grade misfire'. That sounded ridiculous to me. My engine seemed to be running smooth and I was sure it was my transmission. However, the more I thought about it, the more I thought I better make sure. So, I took my truck out for one more spin and made my truck start doing the overdrive shudder again. That time, my check engine light came on. (It had not done this before.) So, I pulled over and read the code and I got the message P0308 #8 misfire. At this time, I was sure that was my problem - and in doing more research on here, found that it was most likely the COP (coil) on my #8 plug. So, the next day, I went and bought the COP from Autozone and replaced it. I then went for a drive, and my truck seemed fixed.

For about 24 hours, my truck seemed fixed. But then, I started having the issue again. It even seemed to be a little worse now. So, I started questioning if I had chose the wrong plug. I had changed the COP near the firewall on the driver's side. Could it have been the one on the passenger side? Everything I found seemed to reiterate that I had chosen the right coil.

So, I deduced that I probably needed to change my spark plugs. Even if they weren't the problem, I was at 82k and it would be time to do so soon. However, as a long time lurker on this site, I was not too eager to tackle the job. So, I checked around at some dealerships in the Oklahoma City area. Most of the dealerships charged around $400 and didn't mention anything about the possibility of breaking plugs. When I asked, they were then happy to tell me that they charged $50 per plug that broke. (I even had one that said $100 for the first, $50 for each one after that.) But the dealership nearest my house quoted me $600 and informed me that it was because the plugs were breaking. They said that their rate was $600, and it would not go up, no matter how many broke. I chose that dealer because I wasn't so sure that the other dealerships would be completely honest with me if they did only break 1 or 2 of my plugs. So, I made an appointment to get my truck in to have it diagnosed for my problem. But I couldn't get in for several days.

I still was contemplating doing the job myself; on most things, I do. So, I checked with my local parts places and found that Oreilly Auto Parts had the Lisle tool. They were the only one that did and they wouldn't 'loan' it out, as they do with so many other parts. With buying that tool, my plugs, and a few other things I thought I might need for the job, it was going to cost me $200 just to do it myself. With all of the headache many others have experienced, I decided I'd just wait and see what the dealership said.

During the remaining days leading up to my appointment, I had begun to notice the truck getting worse and even noticed that when I'd put the truck in 'Park', from having it in gear, my rpms would drop down below the idle speed and then go back to the normal rpms.

When I finally was able to bring the truck in, the dealership diagnosed the problem as a #8 misfire and that I needed new plugs and that my #8 COP was bad. I told them that I had replaced that COP just about a week ago. They told me that the plugs probably made the new COP faulty shortly after I installed it. (This kind of made sense to me, since my truck seemed to run fine for a short time after I replaced the COP.)

The dealership quoted me a total of $780 for the 8 plugs changed, the 8 boots, and the one COP. I went ahead and OK'd the charge and told them that I wanted the plugs so that I could show my bro-in-law and father (who both have this same engine in their vehicles) and the coil (because I thought I might be able to get my money back from Autozone on it).

When the dealership called me to tell me that my truck was ready, they told me that they broke 6 of the 8 plugs. They gave them to me, along with the coil. (As a side note, Autozone did refund me my $45 for the COP that Ford took off of my truck.) This is Day 2 since getting my truck back from the plug change and it's still running fine. I think it's fixed now.

Like I said before, this forum has been a lot of help for a lurker like me. I wanted to put this out there, incase anyone else has the same symptoms. If you are, drive the truck and make it shudder. Then watch the dash for the CEL. If you eventually can make the light come on, I'd venture that you're having the same misfire from one of your cylinders.

I would have bet $100 that my transmission was the problem. And even though I still cringe that I paid $800 for a simple plug change, I'm still glad that it was the problem instead of the much more expensive transmission. And then, I'd still have to replace the plugs soon.

 

When I bought my truck 3 months ago I had the exact same thoughts about it being the transmission, but it was the plugs instead. I don't know how it could cost you so much if you would've done it yourself though, I did mine for under $100 with a brand new Liste that I never even opened.

 

The plugs were $8/piece and the Lisle tool was $100. Then, I was going to need a few various tools that I didn't have.

So, were you getting the shudder only in OD too?

 

Yeah I was, just at lower RPMs (13-1400ish) and under load. I was awfully concerned until I got to thinking about how instantaneous the little jerks were, so I concluded that it couldn't be the trans

 

I had the exact same problem. Swapped in a new set of Motorcrafts and all is well

 

I had the same shudder in over drive and outta over drive when ever the truck was under a load. i bought plugs/wires, two coils (were bad) and the removal tool from rock auto for about 175 i believe. It solved the problem right off the bat.

 

Part of the reason that ford changed its mind and lowered the mileage requirement on a plug change to 60,000 miles......

 

I was having a similar problem a couple weeks ago. While driving in OD 45-55mph my truck felt like the transmission slipped 5 times on the way to were I was going. It didn't do it on the drive home. I thought for sure it was the transmission. I took it to my local (trusted) transmission shop and he drove it and said it seemed like a misfire and then showed me what it was doing. So that evening I ordered the lisle tool, plugs, and nickel A/S and changed them about four days later. No problems at all since I changed them. I had 70,000 miles but I was glad to go ahead and get that nightmare over and done with.

 

Sorry to re-dredge an old post but I wanted to add to this for all those who may come across it.

Everything tha OK04FX4 has said is true ***BUT***, if you can't get your CEL light (trouble light) to come on.. GO GET THE TRANSMISSION CHECKED!!!

I have had the exact same problem in my truck for a while. Everyone I talked to and whom test drove it said the same thing, "oh, it's electrical; it's your plugs; it's your coil over plugs" followed by "wait until it throws the code so you can see which cylinder it is then replace all your plugs and that cylinders coil". So.. I waited.

I kept taking it back to see if it was throwing a silent code while the problem kept getting worse. I couldn't even get it to recreate for a mechanic until it was CONSTANT. Well, as we speak my truck is at the garage with the tranny out getting rebuilt. Turns out is was an issue with a the torque converter locking up.

My truck only has 70K on it and the fluid even remained bright red but in the bottom of the pan I had heavy clutch material sediment. My clutches were TORN UP!!!

So to wrap up.. try what he recommends *BUT* if the light never shows... get a professional diagnostic before it costs more.