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How to retro-fit the rear subframe harmonic damper from the Audi A3 Saloon (2013->)

golfdave

Autocross Champion
Location
Scotland (U.K.)
Car(s)
Mk7 Golf GT Estate
Disclaimer:- This info is for community usage. I am NOT affiliated to, or sponsored by, any company/individual to promote them or their products. Companies/individuals may NOT use my name, photos, or threads/technical guides, for financial or personal gain (fraudulent misrepresentation).

Part 1 of 4
Vehicle used in this guide

UK spec, 2014yr model, Mk7 Golf Estate (GSW), GT (Highline) trim, 1.4lt TSI (140PS) CHPA petrol engine, MQ250 6speed manual gearbox, multi-link rear suspension.

Vehicles that this guide is applicable to
ANY front wheel drive VAG (Audi/Seat/Skoda/VW) car from circa 2003 (Mk5 Golf onwards) with the PQ35 (A5) or MQB platform, with the multi-link rear suspension that has the two holes pre-drilled in the side of the “saddle” section of the main cross beam for the sub-frame. The AWD (Haldex) cars have a different rear subframe so this will NOT fit.

Introduction
I have suffered for the past few years from the dreaded "log rolling" sound coming from the rear, which occurs at low speeds over rough tarmac. I have repeatedly checked the whole rear suspension & have now had 3 MOTs (1 every year) which have thoroughly inspected the rear suspension & given it the all clear, each time!

Research
Searching for solutions initially lead me to a thread about the Skoda Mk3 Octavia which has the same MQB platform. This thread is mainly about the rear hatch opening, however it does start to go into the suspension noises & possible solutions by fitting "harmonic dampers" here:-
https://www.briskoda.net/forums/topic/294540-low-frequency-boom-in-cabin/page/57/

Reading these posts there are further links to "build threads" on the “drive2.com” Russian forum where people are using parts from Volvo, Ford, Mazda, Kia, Hyundai:-
https://www.drive2.ru/l/481661135708226019/
https://www.drive2.com/l/7433929/
https://www.drive2.com/l/9795116/

I then finally found this post on the “drive2.com” Russian forum here:-
https://www.drive2.com/l/533015750428852482/

The item is a VAG made harmonic damper, to cancel out resonant harmonic frequencies generated in the rear sub-frame.

I have never seen this in the MK7 Golf ETKA parts diagrams, yet the Audi A3 that this is fitted to at the factory uses the same rear sub-frame. The first three digits of the part number starts “1K0”, i.e. the part was first designed for the MK5 Golf! However, I cannot find the part being used on any VW, Seat, Audi, Skoda, with it first appearing on the MQB Audi A3 saloon (2013->):-
https://audi.7zap.com/en/ca/audi+a3+s3+sportb+qu/a3/2013-745/5/505-505002/

I can only conclude that when VAG designed the rear multi-link suspension that they designed the balance weight (harmonic damper) to remove the natural resonance that this design of independent rear suspension has. However, the bean counters decided to remove it due to cost yet still have ”acceptable” NVH (Noise Vibration Harshness). Obviously, the Audi A3 saloon bodyshell amplifies the noise more than other bodyshells, so the part was fitted to it. So, having a different bodyshell means we don’t really need it??? The following threads say otherwise & there is a problem with noise from the rear suspension:-
https://www.golfmk7.com/forums/showthread.php?t=18855
http://www.vwgolfmk7problems.uk/mk7_golf_rear_suspension_noise.html
http://www.golfgtiforum.co.uk/index.php?topic=274060.30

Even Bilstein are getting in on the act here:-
https://www.bilstein-shocks.co.uk/blogs/news/vw-golf-mk7-knocking-rear-suspension-problem

It appears the dampers & top mounts are the source of the noise. There is "dimension tolerance" where the damper rod thickness might cause it to hit the inside of the top mount under movement. This causing the noise which then reverberates through the damper body, with the sub-frame resonating & the bodyshell amplifying it!

It does not help that this 2WD multilink suspension on the MK5/MK6 Golf, & MQB MK7 Golf, A3, Octavia, etc., DOES NOT have rubber bushes between the rear subframe & the bodywork where they bolt together (unlike the AWD versions & the Passat etc.) It also appears that you can swap the dampers & top mounts for other brands (including Bilstein) & the noise will “disappear” only to return after approx. 2,000miles once the new parts have “bedded” in.

Therefore, you can conclude that this design of rear multi-link suspension has a design flaw which can only be resolved by fitting the harmonic damper, which is why it was originally designed when it was first introduced on the MK5 Golf. Just the VAG bean counters said NO to fitting it!!
 
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golfdave

Autocross Champion
Location
Scotland (U.K.)
Car(s)
Mk7 Golf GT Estate
Part 2 of 4
Parts required

VAG ETKA illustration for Audi A3/Saloon/2013/Rear Axle/Support Frame/No.505-002

Parts list & approx. costs in UK £
Item No.6:- 1K0 505 563,
Balance weight, £58.65 (x1)
Item No.7:- N 901 838 03, Hex collar nut self-locking M8 (A03G), £0.81 (x2 quantity)

Rear subframe harmonics damper ETKA reduced.jpg
 
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golfdave

Autocross Champion
Location
Scotland (U.K.)
Car(s)
Mk7 Golf GT Estate
Part 3 of 4
Fitting

Safely jack up the rear of the car to gain access to the underside of the rear sub-frame. Clean the metalwork around the two existing holes (I used WD-40). Insert the weight into the hollow section of the “saddle” in the top mid-section of the sub-frame cross beam. Tighten the nuts (using a deep type, 13mm hex socket) until they just touch the subframe, then torque up.

There is “position tolerance” as the holes in the sub-frame are slightly bigger than the “screw studs”. When looking at the nuts (from underneath & looking towards the rear of car) I did the right one up first until the nut touched the subframe. I then used my left hand to hold the balance weight down in the left hole & did the left nut up tight. Then I torqued them both up to 18Nm (13.3lbft)

I do not know what Audi state for the specified torque settings, & VW state 20Nm (14.7lbft) plus 180deg turn when they use the same nut on the rear anti-roll bar drop link. The M8 screw studs are marked “8.8”, so M8 size, grade 8.8 steel on my torque tables state 18.2Nm (13.4lbft) for thorough lubrication, 23Nm (17lbft) for minimal lubrication, & 27Nm (20lbft) for no lubrication (dry). I decided to spray the threads thoroughly with WD-40 & torqued up to 18Nm (13.3lbft)

Just a word of warning about the part. Make certain that the screw studs are parallel with each other & at 90deg to the metal back bar & the rest of the weight. The first one I bought (from Audi dealer) wasn’t & I didn’t notice. On fitting the part, one of the screw studs snapped in two at 18Nm as it could not straighten out due to the metal back bar holding it at the wrong angle! The dealer’s parts dept ordered me a new one & agreed the original one was faulty.

I have retro-fitted the full width Passat rear axle cover, & the two items do not interfere with each other where the Passat axle cover clips into the top section of the rear subframe saddle. Please also note that the yellow coating on the item in the photos is "Waxol" wax spray on protector which I applied to the top section of the item before I fitted it & then I thoroughly coated the whole area after taking the photos.

Rear subframe harmonics damper mod.jpg
 
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golfdave

Autocross Champion
Location
Scotland (U.K.)
Car(s)
Mk7 Golf GT Estate
Part 4 of 4
Results

Now enjoy a much quieter car! Over rough tarmac the car would have more resonance which has now been reduced by 3/4rs. When driving over potholes, bumps etc, the previous double-knock after noise/echo has all gone! On smoother roads the potholes/bumps are now sounding like soft but crisp drum hits, & the rear is far quieter also! Generally speaking, it is as if the volume control for the noise has been turned right down!!

Conclusions

Again, yet another perfect example of serious penny pinching from the bean counters at VAG by not fitting a more expensive, but more functional item to "lesser" VAG cars! I wonder how many people have complained to VAG over the years about strange noises from the rear of the car? How many have had rear dampers replaced time & again only for the noises to return once the new dampers have “bedded” in?? VAG, remove the bean counters as they are costing your reputation & ruining otherwise problem free cars!!
 
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George Ab

Drag Racing Champion
Location
Pacific NW
Dave,

Thanks for the research, clear discussion and DIY. $67.79 all in for balance weight and nuts via economy shipping with e-acca. I have Koni sport struts with VWR springs and no knocks, but always looking for ways to get a quieter ride. This may inspire to me to finally install the aerodynamic under trays and stone guards that have been sitting around for a year awaiting installation.
 

Sc629

Go Kart Newbie
Location
IN
Wow this is great! I plan having my car in the air soon for brakes so I’ll definitely get this done while I’m at it!
 

southpawboston

Drag Race Newbie
Location
Somerville, MA
Thanks, Dave. I'll order these up and install them when I do the passat rear axle cover next spring... The rear suspension resonance has bugged me since my GSW was new. Where I live the pavement is in really poor shape, I'm constantly dodging cracks, frost heaves, and poor patch jobs to avoid the noise! (and wear and tear to the suspension!).
 
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southpawboston

Drag Race Newbie
Location
Somerville, MA
VAG, remove the bean counters as they are costing your reputation & ruining otherwise problem free cars!!

In Autogefuehl's recent preview of the new Mk8, Thomas chides VW for doing away with the hydraulic hood struts. It's clear he's disappointed by the cheapening of the standard.
 

golfdave

Autocross Champion
Location
Scotland (U.K.)
Car(s)
Mk7 Golf GT Estate
In Autogefuehl's recent preview of the new Mk8, Thomas chides VW for doing away with the hydraulic hood struts. It's clear he's disappointed by the cheapening of the standard.

I noticed that......however if you look at the production videos for the MK8 they are fitting the Audi A3 aluminium front subframe as standard....all "weight saving"....
 

anotero

Autocross Champion
Location
Hither and thither
Car(s)
Mk7 GTI
Dave, do you know if all mk7's have these holes in the rear subframe? I know, I know, I could have checked myself, but I was too tired today to get my car up on ramps to check.
 

golfdave

Autocross Champion
Location
Scotland (U.K.)
Car(s)
Mk7 Golf GT Estate
Dave, do you know if all mk7's have these holes in the rear subframe? I know, I know, I could have checked myself, but I was too tired today to get my car up on ramps to check.

99% certain that ALL MQB cars that have the multi-link rear suspension have the two holes....1% doubt just in case of a VAG "unicorn" screw-up!!

& you don't need it on stands...just lie on floor & point camera under & up..that's what I did beforehand!!
 

anotero

Autocross Champion
Location
Hither and thither
Car(s)
Mk7 GTI
99% certain that ALL MQB cars that have the multi-link rear suspension have the two holes....1% doubt just in case of a VAG "unicorn" screw-up!!

& you don't need it on stands...just lie on floor & point camera under & up..that's what I did beforehand!!

I tried. Either I'm too fat or my phone is eating all the bread at my house. :)
 

riceburner

Autocross Champion
Location
West Chicagoland
Car(s)
MK6 and MK7
super cool!

From what i'm seeing it's more in the ~$100-130 range here in the states. But if it's anywhere near as good as the OP suggests, I may just have to do this. I don't hear the knocking sound often but i'm sure this does more than help for that.
 

southpawboston

Drag Race Newbie
Location
Somerville, MA
super cool!

From what i'm seeing it's more in the ~$100-130 range here in the states. But if it's anywhere near as good as the OP suggests, I may just have to do this. I don't hear the knocking sound often but i'm sure this does more than help for that.

Order from e-acca, will come to about $70 shipped if you aren't in a hurry...
 
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