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Car Shudders between 30-40mph and 55-60mph

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8
9
Exp. Type
Drag Strip
Exp. Level
Under 3 Years
United Arab Emirates
Model: V6, 2015 S550 Convertible.
Mileage: 97k

Its an intermittent kind of shudder that comes for 1 sec and then goes and come again if the car is in the same speed range.
It starts at 35mph to 40mph during which the passenger seat and rear view mirror shudders/rattles along with the frame connecting to the soft top.
After 40mph it is not felt as prominent, and once it reaches 55-60 mph it is felt again intermittent after every second or 2, it comes and goes with intensity varying. Even when i lift off the gas pedal and put car in neutral and the speed range is same as above, it will produce this shudder/rattle. While braking there is no vibration, or movement to any side, the car remains straight.
Not related to engine RPM, i tried in neutral as well but it was still there. It is felt irrespective of the RPM and Gear.
In my opinion, it can be any of these things;

1. Drive shaft imbalance or U Joints needs repairing, center bearing is worn, it is a two piece driveshaft and problem can begin in the center connection.
2. Torque converter shudder. (Recently changed trans fluid for first time, and the technician didn't do a good service as the fluid was not checked on HOT Temp 85-95 C, and i drove 2,3 days which may have damaged the transmission. Then i felt like the transmission is not transferring enough power and the sound was kind of different, when i checked the fluid was not even on the dipstick, then i added 2.5 liters of Mercon LV, I checked while car in P and engine started, transmission oil temp was 93 C, and shifted through all gears and leveled the oil. The shifting is kind of strange now :( i think i screwed the transmission while driving with less oil.
3. Maybe the brake pads do no retract fully and stays intact slightly? The front pads were cleaned, and when i drove the car for first 10,15mins it was very smooth like coasting with minimal rpm and ready to launch at any moment.
4. Any bent in the wheels?

Front suspension including control arms, tie rods, link rods, stabilizer assembly, struts are all changed but no effect on the shudder/rattle felt above.
 
6,360
8,180
I'm going with the trans shudder, my F150 does this once in awhile, make sure the right ATF has been installed, and dump some Lucas in it. In it's defense, it has over 180K of hard miles on it.
Drive shaft would be choice 2
Wheel balance #3, however, that is the easiest to check.
good luck with it, let us know.
 
8
9
Exp. Type
Drag Strip
Exp. Level
Under 3 Years
United Arab Emirates
Worn out rear shock(s) letting the wheel hop around? The symptom of that is usually a non-continuous low frequency vibration.
Maybe. But the front shocks I changed didn’t make any difference. And the rear suspension is stiff. The control arm bushings are worn and the shocks are already above their life (70k miles). I will go with the Trans and driveshaft first.
 
8
9
Exp. Type
Drag Strip
Exp. Level
Under 3 Years
United Arab Emirates
I'm going with the trans shudder, my F150 does this once in awhile, make sure the right ATF has been installed, and dump some Lucas in it. In it's defense, it has over 180K of hard miles on it.
Drive shaft would be choice 2
Wheel balance #3, however, that is the easiest to check.
good luck with it, let us know.
This shudder was present before the Trans oil change, and it didn’t make any difference, although the shifting has changed a bit due to driving on low oil for few days. Low probably by 2.5 litres.
For the lucas should i extract some atf then pour the lucas ?
also previously i have experienced, that anything i keep in the passenger front or rear seat, it starts vibrating around 25mph and when it goes to 35-40 i feel it adds second degree of vibration at that point which is prominent. The problem is when there are passengers in the car and soft top is down, i cant feel a single shudder, it gets smooth. But when i am driving alone with the soft top closed, i can fee every single vibration.
So the same 2nd degree vibration is felt around 55-60mph as well. On a hot sunny day as in middle east, all vibrations are felt very prominent (maybe the tire pressure increases due to heat).
The mechanics here do not understand this, and i am planning to purchase the NVH app and test my car! Any suggestions?
IMO the drive shaft balance/ angles has to do something with this.
 
6,360
8,180
I'm not familiar with your specific transmission, it may not have a dipstick that can be accessed from the engine bay. You will have to raise the car (level) and then remove the large nut that will provide access to the trans fluid, normally, there is a dipstick on that large nut, you will see when you remove it. You can then evaluate how much fluid is in the trans. Over filling by a small amount is usually not a very big deal, but you should remove some fluid if you intend to add the whole bottle of Lucas. Adding the Lucas product has been proven to prevent "converter shudder" in a lot of cars, and remember, the trans is somewhat intuitive in that it will compensate for weight, and drag in order to be more economical.
IF you can raise the car on a 4 point lift, you can start and run the car, observing the driveshaft, that would be my recommendation there. You may also take a large pry bar and check for any broken mounts on the trans or engine while the car is on the lift.
Vibrations are very hard to track down.
 
8
9
Exp. Type
Drag Strip
Exp. Level
Under 3 Years
United Arab Emirates
So today we checked the driveshaft and it had slight bend and play in the centre coupling area, which as per the mechanic is the main reason for vibration. Will replace the driveshaft soon and see if the vibration is still there.
will keep you posted.
 
8
9
Exp. Type
Drag Strip
Exp. Level
Under 3 Years
United Arab Emirates
A slight bend in a drive shaft is a bad thing. Glad you found the problem.
What shaft will you be using when you replace the stock unit?
One piece aluminum/carbon fiber driveshafts are not available in U.A.E, importing is expensive and will take 3 weeks.
Stock d/s is available with Ford center. So i will be using a new one same.
 
8
9
Exp. Type
Drag Strip
Exp. Level
Under 3 Years
United Arab Emirates
Any clues for that bend????......Hard acceleration???....I've never heard of a bent driveshaft before................
Maybe.
As this car is imported from U.S and it was driven 90k miles there. Since my purchase, the vibration was already there. But first i tried fixing suspension, tires, balancing etc and now the final thing to fix all vibrations is left with the drive shaft. Its a project mustang for me 😀
This is my first car and i have learnt much while experimenting with it
 

302 Hi Pro

Boss 302 - Racing Legend to Modern Muscle Car
2,009
441
Southeast
Bustshmuch:

Welcome to the TMO Forum. Please keep us updated on your progress with your project 2015 Mustang GT 5.0.

All the best.
 
343
300
Exp. Type
Time Attack
Exp. Level
Under 3 Years
Bulgaria
Hi.
so i changed the driveshaft, rebalanced all tires. Car still shudders badly exactly at 58-60 km/hr 🤦🏻‍♂️🤦🏻‍♂️🤦🏻‍♂️
Is your transmission ok ? My car had a very annoying noise at 60 km/hr which turned out to be a transmission that was leaking did it at every gear and with both clutch on and off. We changed all bearings at the transmission, fixed the leak, filled with new fluid and car is fine now. Also check your wheel hubs at the back as well as shutter could be caused by bad wheel hub / CV Joint which could be caused by a band driveshaft.
 
8
9
Exp. Type
Drag Strip
Exp. Level
Under 3 Years
United Arab Emirates
Changed front wheel hub, both sides.
50% vibration is gone.
front passenger side bearing installed was not even from ford. Some other third party bearing was installed by the previous owner. The right side was hit in an accident, so i think he tried to fix it with cheap parts.
As of now, i will change the left side rear bearing as well. As that side howling sound is still there. And i hope it will fix the problem completely.
the car was driven for 40K plus miles on wide 19” or 20” tires and then changed back to stock size and 18”, due to which the rear wheel bearings might be damaged.
 
343
300
Exp. Type
Time Attack
Exp. Level
Under 3 Years
Bulgaria
Changed front wheel hub, both sides.
50% vibration is gone.
front passenger side bearing installed was not even from ford. Some other third party bearing was installed by the previous owner. The right side was hit in an accident, so i think he tried to fix it with cheap parts.
As of now, i will change the left side rear bearing as well. As that side howling sound is still there. And i hope it will fix the problem completely.
the car was driven for 40K plus miles on wide 19” or 20” tires and then changed back to stock size and 18”, due to which the rear wheel bearings might be damaged.
Sorry i have same problem with left rear wheel hub and even ordered halfshaft as I have all symptoms of a bad CV Joint hopefully this will fix my issues.
 

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