Good Vibrations

Hi.
I think my car (a 2006 A4 Avant 2.0 TDI with 170 horsepower, made in Germany) is going to be a "never-ending story."
Here are the issues I've been experiencing, and some of the things I've already taken care of.

At a speed of approximately 130-140 km/h, I experience very strong vibrations (it feels like sitting on a vibrating platform).
The steering wheel also vibrated.
The front right wheel was making a significant noise while driving at 140 km/h.

The following items have already been done/replaced.

Räder gewuchtet und auch ein anderer Satz Räder ausprobiert. Ka change.
All 8 handlebars were replaced. The two upper right ones had minor damage.
Telescopic rod replaced.
All 4 shock absorbers replaced with Bilstein B6 units.
Swapped the springs for S-line ones. Just wanted to lower it by 2 cm.
Engine mounts (left and right) and gearbox mount replaced.

Current results.
The shaking in the steering wheel is gone, but the vibration at 140 km/h remains.
But because of that, the Audi rides incredibly smoothly again.

I did not replace the tie rod ends.

A master technician at Audi mentioned that the dual-mass flywheel might be causing the vibration.
BUT. He couldn't drive the car because he was still serving registered customers. I was there without an appointment.
Understood.

These vibrations occur regardless of the engine speed. They always happen at speeds between 130 and 140 km/h, even when the vehicle is not in drive.
"So, if I accelerate to 160 and release the clutch, the shaking starts around 140 km/h, but it's almost gone at about 130 km/h."
And of course, the opposite is also true. The same applies when accelerating.

Maybe someone here has another idea.
My ears stop at the tie rod ends.
I'm not entirely convinced about the ZMS (Zero Mass System), or perhaps someone with Audi expertise can share their opinion and confirm if they are familiar with this phenomenon.

Regards,
Bolzer.

Hey Bolzer,

Do you have a Quattro, or am I assuming correctly?
Yes, I once had a faulty driveshaft that caused vibrations at speeds of 110-120 km/h.
There, the storage unit was broken.
I found it using a stethoscope back then.

Sure. Please provide the text you would like me to translate from German to English. I will only provide the translation, without any explanations.

Hi.
No. Unfortunately, no Quattro.
Just a fender bender.
Regards,
Bolzer.

Hi,

How are the brake discs doing?
Is everything okay on the inside? No cracks or rust holes ==> imbalance.

Sure. Please provide the text you would like me to translate from German to English. I will only provide the translation, without any explanations.

I would also check the drive shafts, even without Quattro.
"I had this issue with my Golf 4, and the ball joints on the left side were quite worn."
I would also rule out ZMS (Zero Motor Speed) because it's speed-dependent, and it would stop working when the clutch is engaged.
Let's check the drivetrain.
Greetings.

Hi.
The brake discs are okay; there is no warping present.

The drive shafts aren't making any cracking noises and, in my opinion, seem to be fine. However, I'd prefer to check them again separately. I haven't actually had any problems with the drive shafts on Audis with longitudinally mounted engines before. I've only ever encountered bent drive shafts when they were of different lengths.

Thank you in advance for the tips.

Regards,
Bolzer.

Hi,

Have you checked the seating surface between the rim and the brake disc? I once had some rust stuck between the rim and the brake disc. That was enough to cause vibrations in my car.
I had to remove the rust with a chisel.

Sure. Please provide the text you would like me to translate from German to English. I will only provide the translation, without any explanations.

Hi.
The wheel hub and brake disc are rust-free and clean.
The drive shafts have a maximum axial play of 0.1 mm, but that is acceptable.

New approach. Could it possibly be coming from the transmission?
It seems that way. Are there any potential transmission problems with this A4?

Best regards, Bolzer.

Quote:

The drive shafts have a maximum axial play of 0.1 mm, but that is acceptable. New approach. Could it possibly be coming from the transmission?

If it were a Volkswagen Golf, one might imagine a loose pinion gear. However, I personally have no knowledge of such an issue with Audis.

A faulty constant velocity joint (CV joint) is a possibility. I would start by replacing all the joints from left to right, or the entire driveshaft if the left and right sides are identical. This should only take about 1.5 hours of labor.

The fact that the joints are free of play is not a reliable indicator that they are not defective.
Possibly, the bearing cage (outer bearing) is damaged. In that case, the shaft will no longer be centered.

Hi.
That sounds plausible. However, wouldn't the vibrations have to increase at higher speeds? I was only experiencing it between 130-140 [km/h or mph].

Since I already need to replace the clutch – it's slipping slightly – I'll also change the dual-mass flywheel (DMF) at the same time. While I'm doing that, I can take a closer look at the drive shafts and possibly disassemble them if necessary.

If the vibrations are still present after that, I will replace the gearbox.

I'll let you know when I've replaced the ZMS.
Regards,
Bolzer.

Hi.

As promised, I'm getting back to you.

The clutch disc was completely worn out. I could lift the friction disc about 4-5 mm. The springs are also completely worn.

Apart from a few "phantom vibrations," the car is mostly back to being in good condition.

Regards, Bolzer.

Thank you for the feedback!