A Ford tech's take on "THE CLUNK" (THE ONE and ONLY CLUNK THREAD)

SOCOMech

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FYI the other "CLUNK" threads have been merged with this thread. We absolutely want to hear about member's CLUNK issues and resolutions but we don't need several threads on the topic! Thanks- BIRDMAN
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So by now, most have heard of this horrific and potentially life threatening issue called H.I. ......er, The Clunk. I'm surprised I haven't seen the million threads on it here like another place but, that's a good thing. However, I know there will be, or are, people here who wonder about it. I am a certified Ford tech, even though I actually work as a mechanic for the city now, but have gone through Ford's program and have plenty of credentials and experience working on them at the dealer, just so you know that I'm not some regular dude on here telling you what he thinks about it.

What is it? - A few possibilties have been presented but what most scenarios and symptoms point to is the driveshaft slip yoke, it's that long floppy neck that slips into the back of the transfer case. It has splines inside of it that slip over the splines of the transfer case's output shaft. This area needs grease because it's constantly moving back and forth with even the slightest up down motion of the rear suspension......causing the the axle to go up and down and change angle a bit and so forth. There's a tight seal that it slips into and helps keep everything nice and clean inside. It will also keep somewhat of a vacuum inside so that when you pull the driveshaft all the way out, it will make a small "pop" sound. No, your driveshaft is not going to slide all the way out driving down the road or even jumping it.

"It's a noise in the rear end" - No, it's not. Should it be the slip yoke (and that's what I'm going on here) it's not in the rear of the vehicle it's in the center of the vehicle. Plus, I just have issue with the term "in the rear end"....not because of some traumatic childhood event but because "in the rear end" means the differential or axles. A whining ring and pinion or clutch packs chattering, those are noises in the rear end. The slip yoke may sound like it's "coming from the rear of the vehicle". So when people start throwing out that Raptor's make noises in the rear end, it gives the perception that Raptor's are having differential issues and such.....not the case. (except for the bad batch of axles that made they're way into some first run 5.4 trucks)

"I can't believe I paid $50k for this, Ford and SVT should be ashamed of themselves for not designing the Raptor better" - It is not Raptor specific! This issue has been an issue on F150's since '04, even some other models have had it like Expedition's and even Explorer's. There has been a TSB (technical service bulletin....not a recall) for yeeeaaarrr's. Although I will admit, I wish Ford would have found out what to do about it by now.

"Everyone has it" - Umm, no, not everyone has it. I have a '10 6.2 Super Cab with almost 19k miles.....I don't have have it.....and neither do alot of people.

"Is it on Super Cabs or Crew Cabs?" - Both. '10 and '11. and '09, '08, '07, '06.....see where I'm going with this?

"Does it affect performance?" - No. Some think that it's just grinding away and shaving the splines off, not the case. If anything, there may be very small flakes of nickle coating. Ford says to replace the driveshaft if that happens but do not worry, it is not "hurting" anything. Now I'm no engineer and I'm sure that if it was something simple, Ford would've figured it out by now. Maybe just a loud pop of grease (remember that vacuum?) or could be something else. But don't worry about it decreasing hp or causing the driveshaft and transfer case to fail, not gonna happen.

"What was this TSB about?" - It called for the driveshaft to be taken out and some new grease to be applied inside, that's it.

"I had the TSB done and it came back" - You and other's. But guess what? Some have had the TSB and it didn't come back. It's been a straight fix for some and just a band-aid for others. But remember, not everyone has it.

"But I really do have other noises going on" - Could be other things like the weight by the spare tire coming loose, could be the shock's fluid popping through the bypass ports (more normal when it's cold out.....I live in AZ., it's never happened to me). But most of the scenarios have been when coming to a stop or accelerating from a stop......that's drivetrain related, shocks would be practiacally all the time.


These are just some of the things I see being talked about and wanted to address with my experience. If anyone has any other questions about it, just ask.:005:
 

Madcowranch

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Plus, I just have issue with the term "in the rear end"....not because of some traumatic childhood event but because "in the rear end" means the differential or axles.

This was my favorite part.:jester:
 

SilverBolt

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I wish someone would video tape the slip yoke so we could see what is happening when the noise occurs. I really think it would answer the question of what the heck is going on. My original theory of it being caused by axle wrap is seeming less plausable. When the get re-lubed and the noise is gone shoots lots of holes in my theory. Something that may be happening is that daily driving the slip yoke will only move a small amount. Over time the grease will wear away in that small area. The grease would be pushed forward and essentially start to build up. If the truck then experiences suspension travel beyond it's daily norm it would have to push through the grease build up. Not having my Raptor yet I am obviously shooting from the hip.
 
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SOCOMech

SOCOMech

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I wish someone would video tape the slip yoke so we could see what is happening when the noise occurs. I really think it would answer the question of what the heck is going on. My original theory of it being caused by axle wrap is seeming less plausable. When the get re-lubed and the noise is gone shoots lots of holes in my theory. Something that may be happening is that daily driving the slip yoke will only move a small amount. Over time the grease will wear away in that small area. The grease would be pushed forward and essentially start to build up. If the truck then experiences suspension travel beyond it's daily norm it would have to push through the grease build up. Not having my Raptor yet I am obviously shooting from the hip.

That's a very good theory actually.
 

bfr

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Thanks SoCo.

So my truck is brand new, <500 miles, I've experienced a few weird clunks. Usually seems like right after I've come to a stop...then just sitting there and it happens. Seems like you feel the whole truck move.

Should I ask the Ford dealer to perform the lube at my first checkup?
 

RaptorDDS

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I had the lube job done and it took care of the clunk (yes, opened myself to all kinds of jokes there :hmm:) I also noticed wheel hop when doing a burn out or spinning. This has also been diminished after the lube job. I also noticed if I was doing a brake stand, not letting the tires spin, and then letting off the gas so the suspension would settle back down, it would clunk (before the lube, also better now). Just my experiences. :)
 

peppercorn

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Great write up as always SOCO!

Mine is at the dealer today having the yoke lubed as I have experienced much of what has been discussed.
 
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