Thumping sounds under acceleration at speed?!? [Archive]

prestige.phantom

02-08-2021, 02:27 PM

I am experiencing an odd issue when accelerating at higher speeds. It seems that if I accelerate above ~75mph I get a rather aggressive thumping noise that feels like its coming from the front end of the car. It's violent enough to visibly shake my MMI screen and to be felt in the seats by all passengers. Hitting the traction control off button seems to reduce the thumping a little, but its still noticeable and concerning. I cannot remember the car behaving like this prior to my Stage 1 APR tune, but I have never heard of a stage 1 tune causing an issue like this.

*Motor Mounts were replaced at ~67k miles (at 90k now) so likely not the issue*

*car was aligned last week*

I dont think the car is pulling any error codes, but I'll check again tomorrow...

Anyone have any thoughts?

sepheroth86

02-08-2021, 02:37 PM

I seem to recall mine doing something similar when the front lower arm bushings were bad.

MolonLabe300

02-08-2021, 02:53 PM

I'd check your carrier bushing. Then order this if it's bad.
https://sillyrabbitmotorsport.com/c7-driveshaft-carrier-upgrade.html

Sent from my Pixel 2 XL using Audizine mobile app (http://r.tapatalk.com/byo?rid=87676)

digdah

02-08-2021, 03:27 PM

Where do you hear the thumping coming from? I am chasing something similar on mine but it is so hard to reproduce. Do yours occur all the time you accelerate?

prestige.phantom

02-08-2021, 05:01 PM

Where do you hear the thumping coming from? I am chasing something similar on mine but it is so hard to reproduce. Do yours occur all the time you accelerate?

Very easy to replicate for me. Any acceleration beyond like 10% throttle at high speed and it does it. Seems to mellow out above ~120ish (closed course, professional driver), but that just could be me focusing on driving and ignoring the vibration. It sounds and feels like its coming from the front axle. The sound and feeling reminds me a lot of when my brother's Golf GTI hops when launching because of lack of traction, but obviously my car has plenty of traction at highway speeds. The weird thing is it only happens after ~75-80mph even under the hardest of launches it is smooth up until those speeds.

Wondering If my wheels are out of balance a little and the higher speeds make the vibration noticeable. My shocks, springs, and top hats are all pretty new (less than 10K miles on them).

prestige.phantom

02-08-2021, 05:04 PM

The car was inspected (not for this issue, but just a complementary inspection following my oil change and alignment last week) and the tech reported that tires and suspension appeared too be in good shape upon quick glance.

gk1

02-08-2021, 05:25 PM

prestige.phantom

02-08-2021, 05:28 PM

If the tires were out of balance it would vibrate at speed, not acceleration.
Can you get it to do it at a specific RPM? Does it do it at a lower speed, lower gear but same RPM and acceleration level?
I'd look into what @MolonLabe300 and @sepheroth86 mentioned.

Very good point. It seems to do it throughout most of the rev range, more so speed dependent than anything else (but under acceleration as it only occurs when on the gas not costing).

It absolutely does not do it unless its at least ~75MPH. Doesn't matter if I brake boost or drive causally until that speed its just as smooth as its supposed to be.

Alabama

02-08-2021, 06:43 PM

If the tires were out of balance it would vibrate at speed, not acceleration.
Can you get it to do it at a specific RPM? Does it do it at a lower speed, lower gear but same RPM and acceleration level?
I'd look into what @MolonLabe300 and @sepheroth86 mentioned.

Brilliant! Put the car in manual mode and accelerate in each lower gear to high RPM. I'm assuming if it's the drive shaft the vibration should occur in each gear accelerating towards top RPM, but if it's tire/control arm related the vibration would occur based on speedometer reading, not tachometer reading? I also have the SRM drive shaft carrier, but OP should be aware that JXB Performance sells a competing product.

gk1

02-08-2021, 07:01 PM

Brilliant! Put the car in manual mode and accelerate in each lower gear to high RPM. I'm assuming if it's the drive shaft the vibration should occur in each gear accelerating towards top RPM, but if it's tire/control arm related the vibration would occur based on speedometer reading, not tachometer reading? I also have the SRM drive shaft carrier, but OP should be aware that JXB Performance sells a competing product.

That is what I was thinking...
OP states it has to be above 75mph for it to occur.
Which by rough calculations means...(my calculations could be off)
3rd@6000+rpms(~74mph)....might be hard to do that close to redline
4th@~4500-5000+(~70-78mph)
5th@~3500-4000+(~71-81mph)
6th@~2500-3000+(~65-78mph)
7th@~2500+(~78mph)
8th@~2000+(~78mph)
It would be interesting to see if it is just an issue in 7th or 8th since they are the overdrive gear ratios.
Wondering also about harmonic damper issues I know some early 3.0T's had issues with that, but I would think you would feel that all the time.

prestige.phantom

02-08-2021, 09:00 PM

That is what I was thinking...
OP states it has to be above 75mph for it to occur.
Which by rough calculations means...(my calculations could be off)
3rd@6000+rpms(~74mph)....might be hard to do that close to redline
4th@~4500-5000+(~70-78mph)
5th@~3500-4000+(~71-81mph)
6th@~2500-3000+(~65-78mph)
7th@~2500+(~78mph)
8th@~2000+(~78mph)
It would be interesting to see if it is just an issue in 7th or 8th since they are the overdrive gear ratios.
Wondering also about harmonic damper issues I know some early 3.0T's had issues with that, but I would think you would feel that all the time.

Planning on testing this out tomorrow if the weather is not bad. But from my recollection it occurs in 4th, 5th, 6th, and 7th (don't usually accelerate in 8th because it just lugs the motor, not really the purpose of that gear).

DelayedFlight

03-14-2021, 06:00 PM

Was on the track this past weekend with my RS7. Second track event. By the end of the morning circuits, I was hearing a thumping coming from what appeared to be behind the driver. Had an instructor ride along, and he also thought it was from the left, rear. The thumping was only under power...accelerating with at least half-throttle. Initially above 5500 RPM. If I backed off, the thumping would cease, but as a result I couldn't really push the car.

Had the NGP Racing guys take a look. They checked the hub/bearings for play, but found none. Suggesting it might be a gear bearing case. Drove a few more sessions, but then discovered that it was happening with less throttle, at lower RPMs. The car was physically stable and predictable. Tires and brakes were solid. The noise was not a function of speed. I drove it back home on a 90 minute run. As I got closer to home, it seemed to go away, but then again I didn't push it. I wanted to get home.

I will have to try some sporty driving tomorrow to see if I can replicate. Not reassuring to hear that on the track.

DelayedFlight

03-14-2021, 06:10 PM

Wondering if this is the driveshaft carrier failing/failure that I've now read about on other threads. 🤔

digdah

03-14-2021, 08:23 PM

This is pretty similar to my experience. My problem is I cannot reliably reproduce it but when I do it is only under acceleration. Interesting in your findings.

Was on the track this past weekend with my RS7. Second track event. By the end of the morning circuits, I was hearing a thumping coming from what appeared to be behind the driver. Had an instructor ride along, and he also thought it was from the left, rear. The thumping was only under power...accelerating with at least half-throttle. Initially above 5500 RPM. If I backed off, the thumping would cease, but as a result I couldn't really push the car.

Had the NGP Racing guys take a look. They checked the hub/bearings for play, but found none. Suggesting it might be a gear bearing case. Drove a few more sessions, but then discovered that it was happening with less throttle, at lower RPMs. The car was physically stable and predictable. Tires and brakes were solid. The noise was not a function of speed. I drove it back home on a 90 minute run. As I got closer to home, it seemed to go away, but then again I didn't push it. I wanted to get home.

I will have to try some sporty driving tomorrow to see if I can replicate. Not reassuring to hear that on the track.

prestige.phantom

03-15-2021, 06:44 AM

I recently inspected the front suspension on the car, and it seems good to the eye. I will have to check out the driveshaft carrier.

DelayedFlight

03-23-2021, 06:21 PM

daytona rs7

03-24-2021, 05:57 AM

Audisthesia

03-24-2021, 06:09 AM

A quick update. My RS7 was in the shop today, and the diagnosis was in fact the driveshaft carrier. On most Audi models (as far as I can tell), the carrier is attached to the driveshaft at the time of manufacturing, as such it requires replacement of the entire driveshaft. Estimate from the dealer, parts & labor, was just north of $3200. [o_o] Thankfully, it will be a $250 deductible under warranty. That extended warranty has saved me at least three times. I guess they're losing money on my policy. [:D]

My car is a 2016 with about 57,000 miles, for reference.

Well, if you use an aftermarket to replace it, then this is not true. The OEM carrier that has gone bad will need to be cut off, but both of the aftermarket solutions are 2 piece and install in place over the driveshaft without removing or replacing the driveshaft. The aftermarket ones are also said to be much better by those that have had them installed. And both are way under $3200 ....

https://sillyrabbitmotorsport.com/c7-driveshaft-carrier-upgrade.html $575

https://www.jxbperformance.com/products/c7-driveshaft-center-support-bearing-carrier-upgrade $300

Alabama

03-24-2021, 06:14 AM

there is an aftermarket solution for a few hundred.
cut the old one off.
new one is 2pcs, and stronger.

https://www.jxbperformance.com/products/c7-driveshaft-center-support-bearing-carrier-upgrade

Agreed. I have the SRM version installed by cutting the old one off. I believe SRM has video on their website showing how the OEM carrier allows much more driveshaft play than the aftermarket version. SRM costs more than JXB; I'm not sure what is the difference. Interesting decision: pay only $250 under warranty but get OEM again (that failed), or spend more but for a higher quality solution.

Audisthesia

03-24-2021, 06:20 AM

Agreed. I have the SRM version installed by cutting the old one off. I believe SRM has video on their website showing how the OEM carrier allows much more driveshaft play than the aftermarket version. SRM costs more than JXB; I'm not sure what is the difference. Interesting decision: pay only $250 under warranty but get OEM again (that failed), or spend more but for a higher quality solution.

Yes, good point he had a warranty... But if it goes and you're out of warranty... Aftermarket would be the only logical choice.

DelayedFlight

03-24-2021, 08:55 AM

I would prefer the JXB carrier. From a purely financial standpoint, the OEM replaced under warranty makes more sense. There is a provision in my warranty that prevents double-jeopardy. If this one fails again, it is replaced again with no cost to me.

Of course by then, I likely won't have this car. With the RS7, you either take the hit on depreciation on the front-end of the ownership curve, or maintenance on the back-end. I try to own my German cars somewhere in the middle of said curve.

[drive]

prestige.phantom

03-24-2021, 10:37 AM

Still have not diagnosed my issue. I need to get it to a shop sometime. But out of curiosity in case it is the carrier, I was curious why the SRM is nearly $300 more expensive than the JXB?

Alabama

03-24-2021, 11:45 AM

I was curious why the SRM is nearly $300 more expensive than the JXB?

I don't know. I ordered the SRM for myself before I was even aware of the JXB (SRM had a limited time sale). The design sure looks the same. Maybe the materials are different? Maybe JXB sells more? Maybe SRM is created on-shore and JXB is created off-shore? Regardless, also check the rear differential. My understanding of the problem with carrier failure is not so much that it makes noise but that the extra play in the driveshaft may cause long-term damage to the rear differential.

prestige.phantom

03-24-2021, 11:55 AM

I don't know. I ordered the SRM for myself before I was even aware of the JXB (SRM had a limited time sale). The design sure looks the same. Maybe the materials are different? Maybe JXB sells more? Maybe SRM is created on-shore and JXB is created off-shore? Regardless, also check the rear differential. My understanding of the problem with carrier failure is not so much that it makes noise but that the extra play in the driveshaft may cause long-term damage to the rear differential.

Good point. I am leaning toward proactively replacing the carrier, since it honestly does not look that hard to DIY. If I can save the diff now, then that might be well worth the $300 for JXB

If that fixes my thumping issue then PERFECT. Worst case is that I have accidentally upgraded a common fail-point anyway. Seems like a win-win either way.

Audisthesia

03-24-2021, 12:36 PM

Good point. I am leaning toward proactively replacing the carrier, since it honestly does not look that hard to DIY. If I can save the diff now, then that might be well worth the $300 for JXB

If that fixes my thumping issue then PERFECT. Worst case is that I have accidentally upgraded a common fail-point anyway. Seems like a win-win either way.

Plus, that srm carrier is going to end up black anyhow. May as well go JXB and start thaT COLOR...

DelayedFlight

03-30-2021, 09:28 AM

For edification, here's a photo of my torn up OEM driveshaft carrier. Matches suspected damage to the boot.

https://i.postimg.cc/85DqSgjt/Driveshaft-1.jpg

https://i.postimg.cc/fbY6pRTV/Driveshaft-2.jpg

Alabama

03-30-2021, 07:10 PM

Good pictures. Your car is not very old. Do you have a lot of road salt in your area? Any other idea why the rubber might have deteriorated so badly?

DelayedFlight

03-30-2021, 08:57 PM

Good pictures. Your car is not very old. Do you have a lot of road salt in your area? Any other idea why the rubber might have deteriorated so badly?
I agree. I'm not sure why. The car spent most of it's time in Georgia and South Carolina before I bought it. I may have seen brine treated roads twice, but I keep it clean. It's been at the track twice, and I've put her to task asking for a lots of HP and torque. I think Audi sacrificed here to save production costs, and perhaps wanted to preempt complaints about ride quality. I'd be curious to know if the "performance" variant of the RS7 has the same driveshaft. It might even be the same part number for the A7 and S7.

Alabama

03-31-2021, 06:51 AM

I agree. I'm not sure why. The car spent most of it's time in Georgia and South Carolina before I bought it. I may have seen brine treated roads twice, but I keep it clean. It's been at the track twice, and I've put her to task asking for a lots of HP and torque. I think Audi sacrificed here to save production costs, and perhaps wanted to preempt complaints about ride quality. I'd be curious to know if the "performance" variant of the RS7 has the same driveshaft. It might even be the same part number for the A7 and S7.

Needs someone with more parts knowledge than me. The driveshaft for an S6/S7 for 2013-2018 has part number 4G0521101K. Same part number for A6 but for years 2016-2018. The RS7 has part number 4G0521101M for both base and performance. The RS version costs $100 more than the S version.

gk1

03-31-2021, 05:35 PM

Needs someone with more parts knowledge than me. The driveshaft for an S6/S7 for 2013-2018 has part number 4G0521101K. Same part number for A6 but for years 2016-2018. The RS7 has part number 4G0521101M for both base and performance. The RS version costs $100 more than the S version.

To the best of my knowledge...

4G0521101K is for G1D = 7spd s-tronic (Listed because outside US A6's were available with s-tronic)
4G0521101M is for G1G = 8spd ZF
What the exact difference is I do not know for sure, but I can guess that they are different lengths.
4G0521101L is for 3.0T's with the ZF like the US has.

DelayedFlight

03-31-2021, 07:16 PM

To the best of my knowledge...

4G0521101K is for G1D = 7spd s-tronic (Listed because outside US A6's were available with s-tronic)
4G0521101M is for G1G = 8spd ZF
What the exact difference is I do not know for sure, but I can guess that they are different lengths.
4G0521101L is for 3.0T's with the ZF like the US has.
Good stuff. Yeah, they definitely replaced my beat down shaft with the G1G / 8 Speed ZF variety. I also know that the one from the factory was inadequate! 😄 Good luck to you guys out there with the same issues. I personally think the JXB Performance bearing carriers are impressive. If my warranty didn't cover the existing shaft, I'd have installed that one.

prestige.phantom

04-10-2021, 12:30 PM

Good news: Installed the JXB Performance carrier this weekend (with street bushings) and it performs great. The car definitely feels more smooth and stable under load.

Bad news: my thudding noise / vibration is still occurring.

As of right now I have replaced or addressed the following things

- Drive shaft center carrier (replaced with JXB Performance this weekend)

- Wheels balanced and mounted with new tires (a few weeks ago)

- Car was aligned twice in the past two months (once at its annual service and once after new tires were installed)

- Shocks, springs, top mounts, and their appropriate bushings (replaced with upgraded parts last summer)

- Engine mounts (replaced at roughly 68k miles [at 92k now])

The car has no powertrain error codes. The only interesting thing that occurred when I scanned the car was that neither my Carista nor OBDeleven scan tools could connect to the steering angle sensor module. Perhaps that part is going and causing the power steering to go crazy at random times when under load thus causing a weird feeling in the front end?

Anyway, I think I have exhausted all the usual suspects, so I am probably going to suck it up and get it diagnosed at a professional shop. That or at least have the car scanned with VCDS to see if that brings any more issues to light.

Lmk if you guys can thing of anything, or if there's anything I could do to help it get diagnosed.

vector78

04-14-2021, 07:35 AM

Have you ruled out the wheel bearings? Sometimes they can present problems like this when one of the rollers gets a flat spot on it.

digdah

04-14-2021, 08:27 AM

Have you checked your exhaust to make sure it is snugly on each hanger with not too much play?

prestige.phantom

04-14-2021, 08:36 AM

Have you checked your exhaust to make sure it is snugly on each hanger with not too much play?

Removed and reinstalled all 4 hangers when I had to drop the exhaust to do the center driveshaft support. All of them are correctly attached and secured. The sound/feeling appears to be coming from the front end of the car. At this time, I do not have any reason to think its the exhaust.

prestige.phantom

04-14-2021, 08:38 AM

Have you ruled out the wheel bearings? Sometimes they can present problems like this when one of the rollers gets a flat spot on it.

I have not checked them. They should've been inspected when the tires and annual servicing were done, but its very possible those tech didn't pay any attention to them. I will have to give them a look when I install my new brakes hopefully this week or he next.

sepheroth86

04-14-2021, 01:03 PM

I seem to recall mine doing something similar when the front lower arm bushings were bad.

To quote myself.... I would check the control arm bushings. If they are original. Mine went at around 130k.

prestige.phantom

04-14-2021, 01:36 PM

To quote myself.... I would check the control arm bushings. If they are original. Mine went at around 130k.

I did inspect the front control arms when I was changing the wheels over to the spares a couple of weeks ago. To my eye and touch all of the bushings looked intact and in good shape. No tears, obvious cracking, or other damage. Also, the techs should have inspected those when the car was in for its annual service in February, but again, it is entirely possible they were lazy and didn't pay much attention. I will take another / a better look when I install my new brakes.

sepheroth86

04-14-2021, 02:07 PM

I did inspect the front control arms when I was changing the wheels over to the spares a couple of weeks ago. To my eye and touch all of the bushings looked intact and in good shape. No tears, obvious cracking, or other damage. Also, the techs should have inspected those when the car was in for its annual service in February, but again, it is entirely possible they were lazy and didn't pay much attention. I will take another / a better look when I install my new brakes.

I had a couple of local shops take a look at mine before finally bringing it to a dealership. Dealer tech was able to spot it right away. They sent me a video showing the deflection present in the bushings.

You may have to get a pry bar in between the arm/bushing end and the cradle to get them to move. I had a similar experience with my girlfriends 535i GT. Bushings felt fine by hand but as soon as I got some torque onto them the flaw showed.

prestige.phantom

04-14-2021, 03:13 PM

I had a couple of local shops take a look at mine before finally bringing it to a dealership. Dealer tech was able to spot it right away. They sent me a video showing the deflection present in the bushings.

You may have to get a pry bar in between the arm/bushing end and the cradle to get them to move. I had a similar experience with my girlfriends 535i GT. Bushings felt fine by hand but as soon as I got some torque onto them the flaw showed.

Thats good to know. I will definitely try that! Thank you for the advice!

sepheroth86

04-14-2021, 04:26 PM

Thats good to know. I will definitely try that! Thank you for the advice!

I hope that you find the issue. Best of luck.

Also make sure to let us know what you discover.

prestige.phantom

05-02-2021, 02:16 PM

Update: Had an Audi tech look at my car. He said that while the front lower control arms are starting to fail and should be replaced sometime in the near future, that is not what is causing the vibration, thudding, feeling. He said that something feels out of balance. He recommended I try removing my APR spacers and see if the noise/feeling goes away. If that doesn't solve the issue, then he recommended I get my wheels balanced. I'll update when I try taking the spacers of, hopefully this week sometime.

Gekbi

07-08-2022, 10:00 PM

Any updates on this? My 2014 S7 is having this exact issue!

518Audi

04-07-2024, 08:36 PM

can anyone provide an update as to whether they solved this and how? Having the same issue with a 2017 Audi a6 3.0T. Thumping when accelerating on the highway. Feels like it's coming from the front driver axle/transmission/diff area but it's hard to tell. It's like something is off balance. it lets up when i let off the gas. The harder i push it the more it vibrates. no issue when coasting. No play in the output shaft. Replaced axles and all control arms. The car feels like its struggling to accelerate which is new. I am a little lost here.

Sorry for resurrecting this old thread but not finding any useful information anywhere else.