Differential damper

[GregO]

@Manchild
You get a chance to figure anything out with the vibration ?

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[Manchild]

Not yet. Grasping at straws. Ordered Motul differential oil and will change out when it comes. Did recently install Steeda lightweight G-Trac brace. No change. Have sneaking suspicion problem is with the rear end.

 

[GregO]

Not yet. Grasping at straws. Ordered Motul differential oil and will change out when it comes. Did recently install Steeda lightweight G-Trac brace. No change. Have sneaking suspicion problem is with the rear end.

Been running Motul Gear Competition 75W140 in my Torsen, it's great fluid.
You think it's the rear end. Re-clocking didn't make any improvements ?

 

[Manchild]

Yeah, ordered 75-90. Will put it in when I get it. May not change anything, but can’t hurt. We shall see….

 

[GregO]

Yeah, ordered 75-90. Will put it in when I get it. May not change anything, but can’t hurt. We shall see….

I first used Motul 75-90 for about 30k then 75-140 for 40k.
It won’t change anything.

 

[Cobra Jet]

No reclocking of driveshaft. It is Gulf Coast carbon with no additional flange. Totally balanced (I have the paper). Besides, this is third driveshaft and no noticeable change in vibration at all.
I’m probably a lot older than most of you guys and have built many cars, including 2 Fox Body’s, a ten second 2017 Camaro, and a couple of Corvettes. This annoying problem has me stumped. I really don’t want to get rid of it because otherwise, I love it. It is fully optioned Kona blue with red recaros. Every option sold that year.

Fox owner here as well with many Fox and other Mustangs previously owned. I can feel your frustrations completely. I had bought a then new 2016 PP/6R80/3.55, it too had the same vibrations. In fact there is a thread on here with a few hundred pages of others who had identical driveline vibes. My 2016 was in service in-op so many times that eventually I went through a Ford Buy Back and it was replaced with a new 2018 PP equipped exactly the same only difference being it had the 10R80 instead of the 6R80 and it had a Torsen 3.55.

When the 2016 was going into Ford Service they did everything as such:
- Road force balanced the original rim/tire combo (they kept doing this every time it went in, even though I told them it was not the issue)
- took the original DS and had it balanced (even though according to Ford Service procedures that is NOT to be done)
- replaced the original DS with another factory new DS
- replaced that DS with another new one
- again replaced the DS… so in all, the car had (3) new factory DS’s.
- replaced the front trans flange
- replaced the rear trans flange
- did the Ford “hose clamp on the DS” procedure
- replaced axles
- replaced rear hubs
- gutted and rebuilt entire rear diff
- I spent out of pocket over $1k for new tires/balancing and even when it went in with new tires - they insisted it needs road force balanced and guess what - NOPE.

After the rear diff was rebuilt, it was fine for less than couple hundred miles and the vibe came right back…. I went through (2) Ford Service Centers, the car was discussed with Ford Engineers @ Ford, they even sent a local FSE out to the Service Center multiple times, and they even put the electronic NVH “ears” on it….

At that point this was over a YEAR of the Service Center visits; I was more than patient and was done and demanded the Buy Back. The car was literally down for months at a time where I literally had every new Ford product Loaner that was available…. LOL - they gave me a brand new Ford Explorer ST and when I returned it to them I had put over 3k miles on it… LMAO!

In the event you haven’t hit the main driveline thread, here’s the 250+ page thread here with all the driveline vibe info, FAQ's and DIY fixes available for any S550:
https://www.mustang6g.com/forums/threads/vibration-between-50-70-mph.15990/

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So I do relate to you.

Now for the 2018+ dampener - it is not known why this part is in some 2018+ S550’s and not on others. When I took delivery of my then new 2018 PP w/10R80 and 3.55 Torsen,, upon looking over things I noticed this was a “new” revision to the rear suspension compared to the prior 2015-2017’s. This is the part you are referencing (posted on here by another member, @StangTime): IIRC, it’s mounted at the right side of the rear IRS cradle.

There was an older thread where I had asked other members with a 2018+ to post up if they had this part. Many of the replies back were from M6Gers who had a PP and that dampener part was installed. Does that mean it was only put on Torsen equipped S550’s, I have no clue…. It seems like this was an add-on for PP S550’s, but again the small “query” here really doesn’t tell us the big picture and how/why or total counts of what 2018+ S550’s have that dampener installed.

If you have a 2018+, I think that dampener is a bolt on part as the rear should be provisioned for it. If you’re looking for the part new, reach out to @LevittownFordParts on here and they can get you what’s needed as far as the actual part and hardware.

I know others on here are telling you “nope, that dampener won’t work or don’t do it, etc”. My answer to you would be to yes, try it, see if it makes any difference. It was put there on some 2018+ S550’s for a reason by Ford Engineers, so it has to have some type of relevance otherwise Ford isn’t just going to add costs to their builds and throw on random parts….

It sounds like you have eliminated the factory center support bearing (carrier bearing) since you have an aftermarket DS. So that part is out of the picture (which is another item that causes vibes). Also with your replacement of the factory DS with the aftermarket “balanced” DS, I believe that the term “balanced” is subjective. Sure it was “balanced” at the Manufacturer’s facility and tested on their equipment at whatever load/rpm but even so I would still try rotating it as suggested - because even though it’s built balanced does not mean it will be “balanced” once installed into a vehicle. Use a different color of wax pen across diff flange to DS flange (or number the diff flange and DS flange at the bolts) to mark your rotational tests, this way you know for 100% certain you’ve exhausted the “rotation tests”.

You have taken all of the necessary diagnosis steps and applied them - as well as the replacement of key parts. If after attempting the DS rotation and there is still a vibe - then you’re left with:

- trying the 2018+ dampener
- rebuilding the rear

The only other possible area to check would be the rear diff mounting bolts and the factory rubber inserts. Some M6G members have found those inserts to have been torn OR the bolts sheared.

I hope something above helps; following to see your results and/or resolution.

 

[GregO]

I know others on here are telling you “nope, that dampener won’t work or don’t do it, etc”. My answer to you would be to yes, try it, see if it makes any difference.

I was one of the posters on that 250 page thread that attempted to install the damper on my 2015. After racking the car, dropping the cradle and removing the diff bolt we discovered the bushing wasn’t designed to accept the damper mounting stem. We aborted installing the damper and proceeded to install the Steeda diff bushing kit.
As mentioned several times re-clocking has to be tried even though it goes against the laws of all the components being balanced.

 

[StangTime]

I was one of the posters on that 250 page thread that attempted to install the damper on my 2015. After racking the car, dropping the cradle and removing the diff bolt we discovered the bushing wasn’t designed to accept the damper mounting stem. We aborted installing the damper and proceeded to install the Steeda diff bushing kit.
As mentioned several times re-clocking has to be tried even though it goes against the laws of all the components being balanced.

This is good info. This damper will not fit into the bushing on a car not previously equipped with one. There is a protrusion on the back of the damper that fits into this square hole so it can't rotate. The bolt is also longer to accommodate the thickness of the damper.

 

[Manchild]

Thanks for all the info. I did contact Gulf Coast who hand-made the driveshaft and they don’t think “clocking” will make any difference. Remember, this is third driveshaft and vibration did not change one iota with any one of them. As I said before, I am older than most of you guys and getting under the car without a lift is a problem. My son may be able to help with that, but he is very busy running a business (RT cars), and is no spring chicken himself.
Anyway, I have the damper and the proper longer bolt and may try to install it. Just got the diff fluid delivered and will change it out soon.
Hind sight in 20/20, and I probably should have test drove the car at highway speeds before I bought it, but I was mesmerized by the condition and the fact that it only has 220 miles on it, so I just drove it around the block.
I put the ‘Stang back in the garage for now, and spent the day driving around in my 2017 Whipple supercharged Camaro with meth injection to clear my head. Was at Atco before they closed where the car ran low 10’s at 133. Love that car.
Really wanted to get back into mustangs, and I should Have bought a new one with a warranty.
I have a lot of cars and this vibration in the mustang can be put on hold while I try and figure it out. Any more ideas about the possibility of the damper fitting a car that did not come with it from the factory will be appreciated.

 

[JohnVallo]

In May 2019 I did a lot of experimenting with these Dampers on my 2016 GT350.
I actually bought (2) FR3Z-4A263-A Dampers.
A Longer Bolt was needed, and I had to grind-off the protruding square nubs on the dampers to get a correct fit.
I believe at that time I had a 4.88 Ring and Pinion Vibration.
I first tried one on the Right-Side (Passenger side), as I had seen some OEM ones placed there.
I observed no apparent changes with the one, so I then put a damper on both sides.
I ran these on my car for about 1,000 miles, along with my Home-Made Rear Diff Cover (I also changed the Bolt orientation), with No noticeable difference observed.
I did get some info from a FORD engineer stating that these were placed on certain models for (Harmonic vibration conditions)

See this link for more details (Pictures/Weights, etc.):
https://www.mustang6g.com/forums/threads/vibration-between-50-70-mph.15990/post-2545655

 

[GregO]

I did contact Gulf Coast who hand-made the driveshaft and they don’t think “clocking” will make any difference.

I have a one pc. Shaftmasters with rear Spicer U-joint and they said the same thing that Gulf Coast said to you.
You’ve brough up age as though you’re the OG here, your reluctance to try clocking is a bit myopic. You’ve heard the phrase “Can’t see the forest for the trees”.

 

[NGOT8R]

I agree with what others have said, clock it and see if you get lucky. You may only have to do it once instead of three times to take care of the issue.

 

[shogun32]

If you have a 2018+, I think that dampener is a bolt on part as the rear should be provisioned for it

Mine hit the trash can as soon as I did the cut+replace diff bushings and ditto IRS bushings. Never once thought I had a vibration issue. The giant weight was also on my '19 EB/PP.

 

[Manchild]

I have a one pc. Shaftmasters with rear Spicer U-joint and they said the same thing that Gulf Coast said to you.
You’ve brough up age as though you’re the OG here, your reluctance to try clocking is a bit myopic. You’ve heard the phrase “Can’t see the forest for the trees”.

 

[Manchild]

OK, I should try to clock the driveshaft. Thing is, I can’t physically do it myself. When I get a chance I’ll take it in and have the shop do it.
But, I think you missed my point about multiple driveshafts, and having the exact same vibration at the exact same speeds with each one of them!

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