2025 Mustang GT coupe vibration at freeway speeds

[Lo Pony]

My question is: how do you get them to ‘road test’ something in excess of the posted speed?

They should be able to find a place to get it up to at least 70? Or 75, that’s a common speed limit. Otherwise they’re just looking for a simple out. Maybe find another dealership, sorry to say that.
The problem can be fixed. But it takes someone who really knows what they’re doing and knows what they’re looking for, and who has an idea about how to fix it. I’m not sure if field engineers are very trained in looking for this type of thing anymore. Go back and search for some of my old posts on drivetrain vibration. I used to have a website devoted to this topic, but no longer do.

Sponsored

 

[Lo Pony]

Just a follow up, my posts on this topic were back from 2015 to 2018 in the mustang6G days. I struggled and solved this problem on. 99 IRS cobra, and partially on a 2016 Mustang GT. The dealers wouldn’t touch it.

unfortunately, the structure of the forums is different now, but all my comments were under the warranty, tsb, recalls section.

 

[Frogdog1]

They should be able to find a place to get it up to at least 70? Or 75, that’s a common speed limit. Otherwise they’re just looking for a simple out. Maybe find another dealership, sorry to say that.
The problem can be fixed. But it takes someone who really knows what they’re doing and knows what they’re looking for, and who has an idea about how to fix it. I’m not sure if field engineers are very trained in looking for this type of thing anymore. Go back and search for some of my old posts on drivetrain vibration. I used to have a website devoted to this topic, but no longer do.

If I can do a test drive at 120 before buying one, they can do that to diagnose one. Good luck and let us know.

 

[Lo Pony]

Thanks, I appreciate it! I di recall seeing some stuff on this forum but I don't recall there ever being a fix for it?

The important point to remember is that ideally, driveshafts and pinion flanges are balanced and perfect from the factory. This is never the case. Thus, the objective is to find a position of the driveshaft relative to the pinion flange where the imbalances or defects will cancel and result in zero vibration When the thing is spinning.

The potential fixes are

1) field balancing with weight added to the pinion flange, in the form of washers on the pinion flange bolts most commonly, or hose clamps around the rear of the driveshaft near where it bolts to the pinion flange. This problem isn’t always caused by imbalance, it can be caused by runout of the pinion flange that is not offsetting an imbalance or runout of the driveshaft, or vice versa.. Many times, the driveshaft can be unbolted and rotated relative to the pinion flange to move the imbalance points to a location where they better offset each other. This is generally the first approach to try without adding weight. It can be time-consuming.

2) replacing the driveshaft in the blind hope that the new driveshaft will mate better with the existing pinion flange.

3) replacing the driveshaft and pinion flange as a matched set, which in theory should be the objective when the cars are assembled at the factory.

4) replacing the driveshaft and differential assemblies. This is generally what Ford does. This doesn’t always fix the problem, as a new set has just as much of a chance of vibrating as the old.

 

[Lo Pony]

If I can do a test drive at 120 before buying one, they can do that to diagnose one. Good luck and let us know.

Also, something to remember, is that the drivetrain vibration doesn’t usually show up on these cars until several thousand miles down the road. Which makes me think that there are some tolerances loosening up over time due to some soft part wear, like that rubber giubo damper that is in the rear driveshaft joint that is there specifically to address this problem

 

[Mu2ken]

The important point to remember is that ideally, driveshafts and pinion flanges are balanced and perfect from the factory. This is never the case. Thus, the objective is to find a position of the driveshaft relative to the pinion flange where the imbalances or defects will cancel and result in zero vibration When the thing is spinning.

The potential fixes are

1) field balancing with weight added to the pinion flange, in the form of washers on the pinion flange bolts most commonly, or hose clamps around the rear of the driveshaft near where it bolts to the pinion flange. This problem isn’t always caused by imbalance, it can be caused by runout of the pinion flange that is not offsetting an imbalance or runout of the driveshaft, or vice versa.. Many times, the driveshaft can be unbolted and rotated relative to the pinion flange to move the imbalance points to a location where they better offset each other. This is generally the first approach to try without adding weight. It can be time-consuming.

2) replacing the driveshaft in the blind hope that the new driveshaft will mate better with the existing pinion flange.

3) replacing the driveshaft and pinion flange as a matched set, which in theory should be the objective when the cars are assembled at the factory.

4) replacing the driveshaft and differential assemblies. This is generally what Ford does. This doesn’t always fix the problem, as a new set has just as much of a chance of vibrating as the old.

They replaced the driveshaft and it is as bad if not a bit worse than it was before. At this point I need to contact Ford corporate directly to try to come up with a resolution as the dealer techs aren't capable of troubleshooting or correcting NVH issues.

 

[Mu2ken]

Also, something to remember, is that the drivetrain vibration doesn’t usually show up on these cars until several thousand miles down the road. Which makes me think that there are some tolerances loosening up over time due to some soft part wear, like that rubber giubo damper that is in the rear driveshaft joint that is there specifically to address this problem

As of now it only has 1,500 miles on it!

 

[Lo Pony]

There is a bit early. Do you remember it vibrating from day one?

I forget, refresh my memory. Have they done an analysis with an EVA? A vibration analyzer so to speak? If they’ve narrowed down the problem to the drivetrain and said that they all vibrate and it’s a characteristic of the car, go plead with another dealer to please help you. Otherwise try to fix it yourself, or lemon law that thing and get it out of your hair. It will not get better on its own.

 

[Mu2ken]

There is a bit early. Do you remember it vibrating from day one?

Yes, from the first fwy drive I took it was super noticeable, I was driving it in traffic around town just a bit but never got over like 60 mph until that first fwy drive which was over 100 miles each way.

 

[Lo Pony]

I am so sorry. If you are the mechanically inclined type that has some tools, PM me with your contact information and I can talk you through a typical repair process. If you wanna have a go at trying to address this yourself.

and remind me again, this is a buzz/drone/airplane propeller, subwoofer type sound that is noticeable in the rearview mirror at highway speeds, correct? Not a shake, bounce, or a shimmy, which would be indicative of tires or wheels.

 

[LouG]

The important point to remember is that ideally, driveshafts and pinion flanges are balanced and perfect from the factory. This is never the case. Thus, the objective is to find a position of the driveshaft relative to the pinion flange where the imbalances or defects will cancel and result in zero vibration When the thing is spinning.

The potential fixes are

1) field balancing with weight added to the pinion flange, in the form of washers on the pinion flange bolts most commonly, or hose clamps around the rear of the driveshaft near where it bolts to the pinion flange. This problem isn’t always caused by imbalance, it can be caused by runout of the pinion flange that is not offsetting an imbalance or runout of the driveshaft, or vice versa.. Many times, the driveshaft can be unbolted and rotated relative to the pinion flange to move the imbalance points to a location where they better offset each other. This is generally the first approach to try without adding weight. It can be time-consuming.

2) replacing the driveshaft in the blind hope that the new driveshaft will mate better with the existing pinion flange.

3) replacing the driveshaft and pinion flange as a matched set, which in theory should be the objective when the cars are assembled at the factory.

4) replacing the driveshaft and differential assemblies. This is generally what Ford does. This doesn’t always fix the problem, as a new set has just as much of a chance of vibrating as the old.

If this is true of Ford quality control, I'm surpised they sell any cars at all.
In all the cars I've driven over the last 55 years, most of which were front engine/rear drive, I have never experienced drivetrain vibration as described here. Even the last one, a Toyota 86 which had the NVA quality of a horse and cart, was smooth as silk in the drivetrain up to 200kmh.
Things like runout can be measured, driveshafts can be balanced, I struggle to believe a machined pinion shaft can be out of balance to the degree it can vibrate through the car.
I also doubt that any manufacturer supplies driveshafts and pinion shafts as a matched set. They are made in different facilities and mated at assembly. They are certainly not sold as matched parts.
I'm happy to be proved wrong
BTW Mine has no vibes up to around 180kmh

 

[Frogdog1]

Of course nobody likes to read this word: Lemon Law. Enough on that. It's a thing though.

 

[Lo Pony]

If this is true of Ford quality control, I'm surpised they sell any cars at all.
In all the cars I've driven over the last 55 years, most of which were front engine/rear drive, I have never experienced drivetrain vibration as described here. Even the last one, a Toyota 86 which had the NVA quality of a horse and cart, was smooth as silk in the drivetrain up to 200kmh.
Things like runout can be measured, driveshafts can be balanced, I struggle to believe a machined pinion shaft can be out of balance to the degree it can vibrate through the car.
I also doubt that any manufacturer supplies driveshafts and pinion shafts as a matched set. They are made in different facilities and mated at assembly. They are certainly not sold as matched parts.
I'm happy to be proved wrong
BTW Mine has no vibes up to around 180kmh

Anyone having this problem, please read this post carefully- it is long but contains good information..

Your surprise is not uncommon. I agree with you. I can only speak to this very issue of vibration related to the driveshaft and differential. It is not a quality problem, but a tolerance stack up issue.

History. The 99-01 Cobras were the first Mustangs that Ford built with an independent rear suspension. The IRS sub-assembly is bolted directly to the frame and is very sensitive to vibration. The IRS Mustangs were, and are, notorious for drivetrain vibration compared to earlier Mustangs, trucks, and other cars with solid (live) rear axles suspended from the frame. Those will almost never notice a vibration problem.

I have been through this issue with a 99 Mustang cobra with IRS, and a 2016 Mustang GT, the latter which developed vibration after about 3000 miles, and I partially corrected with the means that I had at the time ( no garage, no tools). I later traded the car in on my 2019 because I don’t have the patience to deal with it anymore. The problem is solvable, but you really need to know what you’re looking for and how to deal with it. And you need to be patient and methodical.

Tech. Driveshafts and flanges are assembled to be as true as practicable, and balanced to be smooth at a certain RPM. Driveshafts and pinion flanges are never perfect. That’s just the way it is. It takes just about 0.5-1g of weight on a pinion flange bolt to throw the whole assembly out of whack and it will vibrate like a turboprop airplane. They are built to allowable tolerances. A driveshaft is just a steel tube with maybe a cardboard and rubber liner inside, with U joints welded on at the front and back. That’s all it is. A certain amount of radial run out, or wobble, is inherent. The idea is to index the two during installation such that the runout and imbalance are offset and mostly cancel out . Back with the 99-01 IRS cars, the fix was that the shafts and flanges were imbalanced but installed as a matched set to cancel each other out. The problem was too common and severe that they had no choice. I don’t think that is practical with the current mass-produced cars.

Usually you can look at the driveshaft and pinion flange and there are some paint dots or colored stickers. These should be lined up when the two are bolted together. And even then it may not completely address the problem. The field service NVH engineers at Ford went through a huge ordeal with vibration in the first IRS cars. Ford has forgotten a lot of those lessons. They tried to address the issue in the 2001 and up IRS Cobras with a better flange and a vibration damper, which was moderately effective, and the exact same band-aid remedy was applied on the 2018 and up Mustangs to address the issues reported for the 2015-2017s! However, in some cars the tolerances add, or stack up. It becomes especially noticeable in cars with a 355, 373 and higher gear ratio, because the driveshaft and flange rotation speeds are faster. With a 315 gear, you won’t notice this normally till you get over 85. With a 4.10 gear, it will shake the fillings out of your teeth starting about 50 MPH.

how does the Camaro avoid this? I’m not sure they do. If they do, I would love to know the answer. What’s the rear end ratio on a Camaro?

If anyone on here is having a similar problem with a 2015-up Mustang, you can PM me and we can discuss approaches to fix it. I benefit none from this, I am only interested in sharing my experience and knowledge to help you.

One last note. Does my 2019 GT PP with A10 vibrate? They all vibrate to a degree. In my case, yes, a little bit above 65 MPH, which became noticeable after 25,000 miles. It’s not bothersome enough to deal with right now, but it’s on my project list. I will first try indexing the shaft relative to the flange, and if that doesn’t work, I will add weight with washers under the bolts where the shaft mates to the pinion flange.

 

[Louis-Stang]

You didn’t notice this on the test drive?

I have a similar problem. Couldn’t notice it on the test drive because we’re not supposed to drive at high speeds until it’s broken in.

 

[Mu2ken]

I have a similar problem. Couldn’t notice it on the test drive because we’re not supposed to drive at high speeds until it’s broken in.

What model and options does your car have?

Sponsored