Hi All, 2008 expy. 5.4L engine.

I've read some threads online which is the only reason why I mention the word shudder. We had a knocking sound a few weeks ago and ended up having the right side cat converter replaced. We went aftermarket. Cost us about $700. While on travel after that fix, I noticed a shudder right around 40 mph.

Interestingly enough, when you accelerate hard thru the 40-50 mph range, it doesn't shake. But if you let off the gas.. let the truck slow to 40mph, and then lightly back on the gas, boom, every time. shake baby shake. It seems to be getting worse. I've noticed it anywhere from 40-50mph. If I keep the gas on light right around 40mph it will shake all the time.

I've heard things like coil packs, etc. Changing the tranny fluid.
However, before I did anything I wanted to see what the group thinks.
This did not happen until that right cat was replaced, for what its worth.

Thanks for the help
Brian from Indiana

 

Did they loosen any motor mounts and/or not tight something back up?????

 

They did not loosen any motor mounts. The only thing we found loose was a u clamp. It was tightened. The problem seems to be getting worse and now happens anywhere from 40pm to 55, 60mph.

I also went to O'Reilly to see if any codes came up on a scan. Nothing. From what I've read here, if there is a coil pack issue, it may or may not show up on a scan.

 

I suggest a Mode $06 scan so you can see misfire counts per cylinder. Mine was a bit sluggish and would sputter like hell under power, but no codes would throw due to the thresholds they set. Cylinder 7 was missing a lot on mine, but generally all were missing, then I pulled the plugs - they were originals with 80k and well worn. (I have an 08 as well).
You might also want to be sure that any sensors anywhere near the work area didn't get knocked around/disconnected.

 

My wife and I decided to take the truck to the local Ford dealer in Bloomington, IN and fork out the $98 for a diagnostic. My goal was to get the mode $06 scan results, minimum.

They called me yesterday and told me it was the professional opinion of their tech that the throttle body needed to be replaced. However, they wanted their tranny specialist to look at it as well. I asked if the mode $06 scan was done, and was told that an EEC test was done as well as some other acronym, but nothing about mode $06. They want $900+ for the throttle body install.

Today, they called back about the tranny. Said it was the torque converter. Want $2250 to replace the torque, seal, pump adapter, filter pan gasket, fluid, and separator plate. I asked about the flush and fill only and was told that the fluid was 'foamy' ... 'like air was getting into the system' and that a simple flush and fill ($199) would not help.

I personally think they are full of crap. Going to get the truck on Monday after I get back in town and then find a place for another opinion.

 

I would get another opinion. Sounds like they want to throw parts at it instead of actually diagnosing the issue. Going from throttle body to torque converter, major difference. Torque converters don't go out from replacing a CAT. They are pretty robust. I would get 2 more opinions.

 

Update..
Took it to a local repair shop... the one that replaced the cat.
We drove it with them. They felt the shudder.

My wife says it is shaking all the time now. Very subtle, but we
can hear the car seat in the back shake (it has a piece of metal on it that makes a noise almost all the time now).

Anyway, the local shop suggested Dr Tranny. Went to O'Reilly and bought that for 7.99 and had them put it in for me. The extreme shudder between 35 and 50mph is still there... but not as bad. But you can definitely tell its still there. Shop said if this didnt do it that the TC was the likely next step.

My analytical mind is telling me this is definitely TC now. If this was a plug, or a boot, then I wouldn't expect any change at all after putting in the Dr. Tranny. But since putting that in, there is a difference. Very light, but it is shuddering. Would anyone agree with that assessment?

 

How many miles?

You replaced the cat because there was knocking sound from one of the cats? But besides the sound, it ran perfectly?

Then immediately after replacing the CAT, the shudder appears?

 

140k.
You got it. No shudder until the CAT was replaced.

Initial noise was a knocking sound that was hard to pinpoint.
Noise eventually moved to a rattle when accelerating in park.
Diagnosed as bad cat after check engine light and code showed up.

It was an aftermarket CAT. Right side only.
Shudder did not exist until CAT was replaced.
Appears to be coincidence.

 

I am not buy the torque converter. And when a shops to make a profit, nothing is coincidence. I bet it's ignition related/fuel.

Have your coils/plugs been replaced? Bad coils will cause the truck to shudder without throwing a code.

 

I bought a single COP and replaced it thru each cylinder, driving after each replacement. Did not replace plugs. Was hoping I could find the single coil pack that was bad, but that didnt happen as for each cylinder I put the new COP into, the driving experience was the same.

 

I would replace the plugs at the least. Won't cost much.

Are you 100% sure the correct CAT was used?

 

So are you suggesting only the plugs, or the plugs and the boots?

No idea if the correct CAT was used. I was told the ford cat cost $1600 and the aftermarket was $700. So I went aftermarket and trusted that the mechanic is ordering the right part.

Any suggestions on how I can find out if the correct CAT was used?
Is there something on the unit somewhere?

 

There has to be markings/serial numbers on the cat. Crawl under there and take some pictures. Then research the cat and see if it's compatible with your truck/state. Post info here and I will see what I can find also.

If the CAT checks out, I would get all new plugs and COPS-the plugs need to be done anyway, the cops won't hurt. Aftermarket is fine.

Also, leave the battery disconnected for 25 minutes at some point. That can't hurt and may clear the adaptive info stored.

 

I'm no mechanic but wouldn't the clogged CAT be a sign that there is a fuel/ignition problem. I pretty sure bad plugs/COP can mess up a CAT pretty quick. My 07 Expedition does the same thing, I changed transmission fluid and it helped with the shudder but didn't fix it. Plugs and COP are next.