TLDR notice: Having possible clutch chatter issues, need help in diagnosing and advice on where to go from here...

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Help me understand what clutch chatter is when experienced on ZF6 7.3 diesel truck and how it might be mistaken for axle wrap. Below is the very LOOOOOOOOOOOOONG back story.

My truck details are in my signature, but for anyone using a phone or tablet, here they are as well.

2000 7.3 short bed super cab w/ZF6 manual at stock height and stock tires towing a 12K lbs 5th wheel camper.

Since buying the truck nearly 3 years ago I have been experiencing what I would have described as axle wrap. Recently I thought I had this problem licked due to replacing or installing all of the parts below.

1. OUO traction bars
2. New OEM rear leaf springs
3. Bilstein HD 4600 shocks
4. Air Lift 5000 air bags

Before installing the OUO traction bars I had axle wrap during 90% of the starts from a dead stop and almost 100% of the time when the start was at an incline or reversing. Since installing the OUO traction bars the axle wrap had gone away and I thought I had won the battle. Over the past couple of months when backing up or even starting on an incline from a dead stop the truck would just go with no shudder. All of this driving to test the traction bars and axle wrap had been unloaded, except for the 45 gallons of fuel in an auxiliary tank in the bed.

Fast forward to Saturday the 11th of February. We were getting ready to tow our 12K lbs 5th wheel for the first time since installing all of the parts listed above. My hopes were high and my faith was strong that the truck would perform much better than it had in the past. It did, until I had gotten to a point at the end of our driveway where the trailer must be backed up 50 yards or so up a slight incline.

This is the first time the shudder in the truck returned.

Towing the trailer in a forward direction for the next 1.5 hours was great. No shudder, no jumping or anything and I was hoping maybe the shudder earlier was a fluke situation and we were still winning the war. The truck did great towing the trailer to the campground, but this is where I started to lose faith.

As we maneuvered the trailer into place both low gear and 1st gear would produce the shudder I was so familiar with and that I hoped had left us for good. Reverse was only shuddered for a short time because of how the campsite is situated though. At this point, I knew I had a problem that still persisted and decided to call for help, which meant contacting OUO.

This is also the time that my steering box exploded just as we were finishing unloading the trailer. Thanks again to Paul (AllaboutMPG) for the help, could not have fixed it without you friend.

Link to the steering box exploding saga below.

https://www.ford-trucks.com/forums/1...ering-box.html

I contacted David at OUO via email and described to him what was going on. He asked me to call him on Sunday, as it was getting late Saturday. I wrote him Sunday morning and told him to enjoy his day with his family and friends and we can discuss the issue on Monday. He promptly wrote back and said that it was not a problem at all and he was eager to help out a customer and to call him when I had a few moments to discuss the issue.

I called him shortly afterward and we talked about what I had described above and he thought maybe I was having a drive line issue. I described to him that the u-joints appear to be original to the truck, and I cannot say that the slip yoke near the rear differential has ever been lubed. Because I don’t know the terminology concerning the drive shaft in regards to 1, 2 or 3 piece and what the different portions are called, he asked that I send him a couple of pictures via text.

Below are the pictures I sent to David.





As you can see, I believe that I have a cardin CV with double u-joints at the front off shaft near the transfer case, a slip yoke about a foot in front of the rear differential and then a single u-joint on the rear differential. I had the u-joints inspected about 1.5 years ago when the rear pinion seal was replaced and the mechanic (shop I trust and have been using for years) said they looked good and he would not change them if they were on his truck.

David called me back promptly after receiving the photos and said that is exactly what he needed to see. He asked if there was a way I could video what was going on with the truck when it was loaded. I told him I could rig something up on the 21st when we leave this campground and move to another for a few days. He was satisfied with that and said he didn’t want to suggest parts yet or start throwing parts at the truck until he saw a bit more of what was going on.

Since then I have been emailing back and forth with David, answering questions and doing what I can to provide more details to someone on the other side of the country through a text format. Similar as I am doing with all of you now.

During the last email I had from David he mentioned he didn’t think I had a u-joint problem, they might be worn but they are not malfunctioning. Same goes for the splines on the slip yoke, they could use some maintenance, but did not appear to be failing. We came to the realization that since the truck performs great and as it should at speed (50+ MPH) then the drive line could use some sprucing up, but is not the cause of my shudder.

I had told him that I had been reading a lot and trying to self educate on what my problem was. I was neck deep into a crash course about drive line systems and the like. He asked that I read up on “clutch chatter” and let him know what my thoughts were. He said “We could have a clutch Issue, that really low speed shuddering when you're letting the clutch out is a symptom of clutch chatter”.

Coincidently another FTE member that I stay in loose contact with via email also suggested clutch chatter as the cause this morning. I began to read up on clutch chatter even though I initially thought that was something to do with noise and maybe rattling coming from the transmission, I was wrong.

This is the first thing I read about clutch chatter.

Clutch chatter is the sudden shudder that occurs when a faulty clutch disk or clutch component is initially engaged. This shudder or vibration may vibrate throughout the entire vehicle. It's often the result of worn or contaminated clutch components.

This sounds dead on to what I am experiencing when I thought I was having axle wrap problems. I have since asked David if “in your experience, will traction bars help the symptoms of clutch chatter, because the shuddering has greatly improved since installing the bars”. I suppose I could have been having both axle wrap and clutch chatter problems and the shuddering improved because the axle wrap problem has been removed which in turn greatly improved the unloaded driving experience.

That was only an hour or so ago, so I anticipate I will receive a response tomorrow or soon thereafter.

When I bought the truck 3-ish years ago there was a receipt in the glove box for a new clutch and install a short while before I bought it. I don’t have the receipt anymore, so any further details of the clutch install are gone. I do not recall it saying the brand or type of clutch and the truck ran well, so I moved onto other concerns with the truck I had at the time.

I will post the video of the shudder during start from a dead stop with the trailer attached as soon as I can, but will probably be toward the end of the month unless I can find a WiFi signal while camping.

My questions to the FTE brother/sisterhood are as follows:

1. After reading this long story, what are your thoughts?
2. Does the shudder my truck is experiencing sound like clutch chatter?
3. Can clutch chatter happen even if there is no audible “chattering/rattling” sound happening?
4. Has anyone had any experiences with clutch chatter they can share with me to help me understand?
5. Can anyone recommend a good ZF6 mechanic/shop in the north GA area (zip code 30643)? I am willing to travel if the shop is reputable, but need to be sure about the problem and the mechanics at the shop doing the work.

In closing, I will be sitting back with a cold beer next to the lake and checking this post every time my wife is not looking (supposed to be on vacation) and look forward to questions or concerns that I may be able to answer. Thank you for participating in this journey of creating the most reliable and hard working truck I have ever known with me.

 

Sous.. If I'm understanding it right, its what mine did with bad clutch components. Mine would(axle) bounce like no other, trying to back my trailer up(8k). Not putting 2n2 together, it was more of a preventative maintenance thing, I replaced my clutch prior to a week long vacation, plugs, that clutch had been in for 100k. To my surprise, I was taken back onto how the heck I made it to my bros shop. Clutch fell apart, springs everywhere, input shaft bearing destroyed..etc... With all new components, the tpedal now is smooth as butter, and no axle hopping when backing up with trailer

 

Thanks for your input. I have just sent off an email to Midwest Transmissions to see if they have anyone they recommend down in this neck of the woods.

I don't have the tools, knowledge or guts to pull the transmission myself.

 

I hear ya. I try and do my due diligence prior to anything that takes me away for any period of time, however, some things fly under the radar. Enjoy ur vacation but in meantime, I'd arm myself with the FITZALL kit(with bearing driver). I'd bet, the input shaft is knarled up. I'm on my second round. Have the 3rd on the shelf

 

Sous,
I didn't think of it the other day when you mentioned the problems with hop but have you checked the bell housing mount bolts. I know of a couple of vehicles, not superdutys, that had shudder/hop when starting off and the bell housing bolts were loose.


I suspect the clutch itself but it's easy to check the bell housing

 

Does it only happen when you are feathering the clutch or does it happen from take off in gear?

If you have a slightly grabbier clutch it will do this. I got rid of my stock clutch for a south bend and tried numerous types of friction all with the same result. Letting off the clutch to back up up inclines, and starting off would shake the whole truck like I was bouncing my foot at friction point adding and taking away power although it did not make any noise just hopped. With heavy enough trailers it would do this all the time in reverse. Keep in mind I had tried reman ZF6s, a brand new one (verified brand new not reman), and also a Ford reman (long story on those).

On tear down for new clutches and inspections there were not hot spots on the flywheel and friction looked good. Never will get a south bend again nor recommend as other clutches did not do it.

Long story short, I ended up selling that truck for a bigger one and only have 1 manual truck left (ZF5). I did not have ladder bars.

 

There are two types (at least) of materials used in clutches. One is something like asbestos or stuff like they use in brake shoes/pads and the other one is ceramic. I know the latter as a button clutch. So named because the ceramic clutches have what looks like several disc brake pads fastened to them and there are large gaps between them. The other style of clutches made with asbestosis type material have the whole face of the clutch plate covered with large discs, probably with radial groves on the face of it. Drivers in general do not like the button clutches because the ceramic doesn't like to slip and the whole truck jumps around while trying to feather your way into a dock. This may or may not be part of your problem but when buying a new clutch I stay away from the button clutches.

 

What type/brand clutch did you install into your truck?

 

Thanks Paul, I will certainly take a look at those in the very near future.

 

It used to happen at most times when taking off from a start when going from neutral or clutch engaged to applying throttle, especially on an incline. Reverse, it was the same thing.

Now that I have the traction bars installed, the shudder has gone away with the truck unloaded, but with the trailer on it is still very apparent.

If I am understanding feathering properly, it is when I slowly disengage the clutch and apply throttle in order to move the truck and trailer. If so, then the shudder occurs during this time, but never when moving from up through the gears. Down shifting is not a problem either like going from 4th to 3rd at 45 MPH. Yes, I do rev match when downshifting and don't let the RPM's bounce all over the place.

I am not sure what brand/style of clutch was installed prior to buying the truck, or if it was ever installed and the receipt was just there as a ploy to help sell the truck.

What you are describing above is how I would describe my truck behaving with the trailer hooked up. It is as if I am applying full throttle and then letting off and doing this over and over again very quickly. Maybe this is just something that I am going to have to live with? It seems very violent though and I trust is not a good thing.

I plan to get a video on the 21st when we leave this campground, but am doing research and trying to find a decent shop to work on the ZF6 if it comes to that for now.

Based on what you know about my situation, is there a clutch you can recommend that I can look into?

I love the ZF6 in the truck and the control I have over the truck when rolling, just not the reaction it gives me when starting from a stop with the trailer.

 

This is all new territory for me, and I would like to have a good idea of what I am talking about when I talk to a shop about what is going on and what can be done to fix it. Thanks for your thoughts.

 

Sounds like clutch chatter to me. I can "launch" hard with mine with stock springs and no traction bars with zero chatter or axle wrap. I have a LUK clutch but there are several good options out there.

 

AC-Delco from Rockaito..112.00std, lol... Everything included but the flywheel.
Yup, when backing up with trailer, it was like driving over the drunkbumps in the median of the road

 

Thank you for your input and stating what sort of clutch you have. This helps me get pointed in the right direction.

 

Just spoke to a guy that has a great reputation for transmission work (including the ZF6) that is about 40 miles distance from where our home is at. He is planning to see the truck at the end of the month when we return home and go over some options.

I described to him what I was experiencing and he mentioned the pilot bearing may be worn. I talked to him about the clutch material causing a problem, and he agreed if it was the wrong application for what I was using it for it could cause shuddering, but he would not know until it the case was out of the truck. He said that we could figure it out when he sees it in person and it should not be a problem to get it sorted out for us.

He was very receptive and we are optimistic about getting the problem resolved. I plan to make a "kill list" of things that I need addressed, so far they are as follows.

1. Identify cause of shudder and resolve it with required quality parts (not southbend)
2. Perform any upgrades/preventive maintenance (clutch, flywheel, input shaft, shift arm, etc) that will enable us to tow our 5th wheel in comfort for the next 100K miles
3. Remove and replace the fill hole plug on the side (currently siezed in place) in order to stop filling from the top of the transmission
4. Check transmission mounts and replace if needed