B6 Front Subframe Bushings Replacement, Fixing the Clunk

[Kevin C]

For a while I have been sorting out the front end on my B6. I have factory sport suspension a H&R front swap bay bar and a RS4 rear bar. Four years ago my ball joints had that arthritic groaning sound so I did a complete front arm kit using Febi parts. After three years I had a clunk on small bumps and the arms were creaking on hot days. That and my OEM sport shocks were shot.

The short story is I did a complete upgrade with Koni FSD shocks and a full Lemforder arm kit. Every arm, tie rod end upper bushing... You name it I was replaced. That included new front wheel bearings and a B7 brake upgrade. Later on I swapped in a S4 rack and did a servotronic upgrade. The results were great smooth, quite responsive steering but I still had a clunk on certain bumps. And whatever it was it was slowly getting worse.

When I got the car it had about 135,000 miles and right now I'm at 172,000. Overall the cars is great it just clunks on small bumps at low speeds and doesn't have the tight feel that it had when I first bought it. Over time the clunk was getting annoying.

Since every other part had been replaced I started to look at the subframe. After lots of reading and finding solution from welding subframes to increase there torsional rigidity to complete new subframes I still wasn't sure what was causing the noise. Some hypothesized that the subframe cracks internally or the the crimps loosen up and welding fixes the issue. Some have had welding improve the problem but it never quite goes away. Mine looks perfect and from the factory the crimps are welded ( you need to look closely). No obvious cracks, it looks perfect.

What I think is happening:

The front bushing of the front subframe bushing have a top profile that looks like a crown. The little peaks give the subframe some cushion and let it gently absorb road imperfections. They end up seeing a lot of motion and over time the peaks wear down. As they wear the road motion is not as absorbed as smoothly and they slam a little. That wears them a bit faster and creates a bit of noise. The peaks on my bushing were pretty worn and you can see marks where they have been rubbing against the casting.

Over time the wear gets to the point where it's allowing the front of subframe to flex a lot more than it was meant to. If you put a new bushing in the subframe flexes a lot less.

That was my theory. Also, I wanted to keep the rubber isolators. Solid bushing are an option, but I wanted to keep some isolation.

Front subframe bushing upgrade.


Replace the front position, front subframe bushing with rear position front subframe bushing. ECS list this as the correct bushing for the front position on a car with sport suspension. For some reason mine did not have them. I also couldn't track my subframe PN (8E0 399 313Q) to any current number. ECS lists it as 8E0399313BG.

I found that the online manuals and AllData had nothing on how to replace the bushing. The section is blank with a note that I will be completed at a later time. I did find that my old Bentley manual for my Passat had the info and showed that Tool # 3372 was needed to press the bushing in. I have heard of people tweaking the subframe trying to press it on on a shop press, the factory tool seemed like the only reasonable solution.

Worn bushing



What its supposed to look like new:




Factory installation tool with sport rear bushing (tool # 3372). There are some other kits that go with the tool, I was able to improvise using parts from oghether puller kits that I own. The key part is the tapered split ring and the notched pressing cups.



New bushing installed ( I know the picture is sideways).



Old VS New:

[Kevin C]

The short story is the bushing made a huge improvement in how the cars feels. Super happy with the upgrade.

[Charles.waite]

Did you consider going with S4 Subframe mounts? I have no idea if S4s use the same front subframes (they look different on a quick ebay browse), but I would assume the bushings are cross compatible. They look pretty similar in pictures.

Really interesting find though, and thats awesome that it helped solve a persistent issue like that clunk.

[Kevin C]

Did you consider going with S4 Subframe mounts? I have no idea if S4s use the same front subframes (they look different on a quick ebay browse), but I would assume the bushings are cross compatible. They look pretty similar in pictures.

Really interesting find though, and thats awesome that it helped solve a persistent issue like that clunk.

Charles,

Good point. I just checked and according to ECS the bushing PN for the S4 and my sport suspension A4 are the same are supposed to be the same ( 8D0399419Q). Not sure why but my front bushings are the standard non sport parts (PN 8D0399415E). I did buy four of PN 8D0399419Q. I guess I will need to do the back bushing next.

[Gosser]

Nice, I always wondered if there were physical differences between the standard vs sport subframe bushings. Thank you for the findings.

More importantly, where did you get that subframe bushing installer from?! I cannot locate a 3372 anywhere. Does it remove the bushing as well? Did you need to remove the subframe completely to do this?

[Kevin C]

Nice, I always wondered if there were physical differences between the standard vs sport subframe bushings. Thank you for the findings.

More importantly, where did you get that subframe bushing installer from?! I cannot locate a 3372 anywhere. Does it remove the bushing as well? Did you need to remove the subframe completely to do this?

I ordered it from Audi - Snapon. It took about a week to arrive. I was able to do the fronts with the subframe in the car, I will post a full write up this week.

https://audi.snapon.com/SpecialTools...ame=Suspension

One thing that I want to figure out is if the subframe itself is different on the sport models, we know that the bushings are. The cost difference of the frames is way more than the cost of the bushings. That and on mine it looks like all the seams are factory welded. I wonder if that's the difference, it would explain why some people are getting welds adde

Quick job outline:

1: Jack up the front end and support the car at the transmission crossmember.

2: Remove the front wheels and both fender liners.

3: Disconnect the wires to the headlight leveling sensor on the drivers side lower control arm.

4: Support the engine with a floor jack and a cushion.

5: Remove both subframe support / motor mount brackets ( Front cast brackets, three frame bolts each plus two motor mount bolts). Disconnect the starters power wire from the passenger side bracket.

6: The subframe will drop down far enough to allow the puller to be fitted. To ease removal make several cuts with a hacksaw blade in the top of the bushing.

7: Attach the puller adaptor and a puller set. Crank the puller drive and the bushing comes right out.

20200112_174048.jpg

8: Reinstall using the tapered guides in the special tool.

I don't have a photo of the initial tool setup to get the busing in. I will get a sketch of it later.

Bushing being pulled in after the guid tool allows gets the top of the bushing into the subframe.
20200112_184259.jpg

9: once both bushing are replaced reinstall the cast brackets and torque to spec.[

[pablolizarraga]

I was able to do the fronts with the subframe in the car, I will post a full write up this week. [

Looking forward to it! Already tons of great info.

Any TTY bolts that required replacing?



Sent from my iPhone using Audizine

[Gosser]

All sub frame bolts are listed as TTY bolts in the bently manual. I have reused many without issue. My only recommendation is to torque them. I've used 90 foot pounds with no issues on many vehicles. I avoid another 180 degree or whatever it is since the threads have already been distorted. I've tried to free hand a few of them and end up with clunks, so 90 it has been since.

[Zolli]

Superb write up!

[jj94tt]

Did you get around to doing the rear bushings on the front subframe? Anxious to hear the results.

I am going to replace the top strut bushings with Audi parts and see what that does. I used Febi the first time around.

[Kevin C]

Did you get around to doing the rear bushings on the front subframe? Anxious to hear the results.

I am going to replace the top strut bushings with Audi parts and see what that does. I used Febi the first time around.

Planning on doing it this weekend. Fyi, I have done the strut bushings twice. First time was Febi and the second time I used Lemforder, no difference.

[jj94tt]

Huh... OE is probably Lemforder... so I guess that'll be a waste of time/money.

[DPDISXR4Ti]

Interesting thread. My car is a sport suspension and for quite some time has had a "groaning" issue when doing low-speed turns. I examined the sub-frame for any weld breaks and didn't find anything. Maybe new sub-frame bushings are in order. Suspension-wise, EVERYTHING is original on the 140K-mile car, so it wouldn't be a bad idea to replace everything. That said, I just don't know if I want that much of a project right now.

You mentioned that you've done the upper strut bushings twice. Did you diagnose a failure there of some sort?

[EuroxS4]

If your gonna go that far might as well go with some poly bushes if anyone makes them. Then again based on your needs poly might transfer too much vibration and noise into cabin. Would be interesting to see if such a bush is available in a poly urethane.

[Kevin C]

If your gonna go that far might as well go with some poly bushes if anyone makes them. Then again based on your needs poly might transfer too much vibration and noise into cabin. Would be interesting to see if such a bush is available in a poly urethane.

The upside of polyurethane for this location is that its a non rotating joint so that the usual poly squeak and wear problem is not an issue. The factory sport bushings are a bit pricey (list is around $80 each, some dealers have them for about $54 I got a set of four for $132 from Europe) but the are a huge improvement over the non sport and still have some compliance. One interesting thing is the convertibles came from the factory with solid bushings. There are also aftermarket kits that convert to solid. It seems reasonable that you can pick up a convertible subframe from a yard. After I have some more coffee I plan on getting the car into the garage this today and giving the rears front subframe bushings a shot.

PN of sport bushing: 8D0399419Q


034 Solid bushings:
https://www.ecstuning.com/b-034motor...-601-0000~034/

[EuroxS4]

The upside of polyurethane for this location is that its a non rotating joint so that the usual poly squeak and wear problem is not an issue. The factory sport bushings are a bit pricey (list is around $80 each, some dealers have them for about $54 I got a set of four for $132 from Europe) but the are a huge improvement over the non sport and still have some compliance. One interesting thing is the convertibles came from the factory with solid bushings. There are also aftermarket kits that convert to solid. It seems reasonable that you can pick up a convertible subframe from a yard. After I have some more coffee I plan on getting the car into the garage this today and giving the rears front subframe bushings a shot.

PN of sport bushing: 8D0399419Q


034 Solid bushings:
https://www.ecstuning.com/b-034motor...-601-0000~034/

Interesting that the convertibles came with solid bushings. 034 looks pretty good,do they provide install instructions and torque specs??


Looks like they can be had for cheaper:

https://www.verkline.com/product-cat...a4-s4-b6-audi/

[Kevin C]

Interesting that the convertibles came with solid bushings. 034 looks pretty good,do they provide install instructions and torque specs??


Looks like they can be had for cheaper:

https://www.verkline.com/product-cat...a4-s4-b6-audi/

That same page also lists poly bushings. The nice thing is you don't need a special tool to install them. I wanted some isolation and the factory sport bushings seem like a good compromise, that said the urethanes while stiffer are certainly easier to install. Some people have had issue with the aftermarket solids not fitting the subframe very well.

[Charles.waite]

Damn I’ve never heard of Verkline but they sell a complete lineup for literally every bushing. That’s awesome. Been trying to find ones for the lower front control arms with mixed success.

[Kevin C]

Back at it today. A quick update. After I did the front bushings the cars handing and road feel was definitely better and the low speed bump noise was way better but it was till there. Over the next few days it came back but not as bad as before and it was now coming from the left side and is further back. The car still has a better road feel but the clunk is back just not as pronounced. In the name of science I figured it was time to do the rear bushing.

Step 1: Get the car in the air. I put the rear wheels on cribbing blocks and jacked up the front to the max height of my jackstands. This is where having a lift would be really nice.

Step 2: Support the back of the tranny and remove the crossmember. The exhaust will need to be disconnected to get it out.

Step 3: Pry the subframe down a bit and hold it in place with a block off wood. Pretty much the same as the fronts. Using an assortment of large nuts and bolts and puller tools remove the old bushing. I didn't find any obvious wear on the rear bushing. Things I did notice is that my 2003 had still had standard bushings in the back, not the sport bushings (my 2003 has sport suspension). It does seem that the rubber on the old bushings is very soft. I'm pretty sure its deteriorated from aging and oil exposure. Any service person looking at the old bushings would most likely say that they were still good, however I'm in to this far and I want to know for sure so the new bushing are going in.

Step 4: Install the new bushing. I came up with a trick of taping the split rings together so that they stay in the guide. It makes the job go a lot faster. Time to change one bushing on my back was about an hour. I did notice some signifigant rub marks on the left side rear bushing, however unlike the front there was obvious clearance. I will update once I get a few miles on the new setup.

Old bushing being pulled out:
20200202_124538.jpg

Sport VS non Sport.
20200202_125352.jpg

Pulling new bushing in.
20200202_131336.jpg

Done!
20200202_133045.jpgi

[DPDISXR4Ti]

Interesting that the convertibles came with solid bushings.

My thoughts exactly. The fact that they came on a production car means they can't make the ride too obnoxious. I imagine they install much easier too - just chuck them in the freezer the night before install.

[DPDISXR4Ti]

It seems reasonable that you can pick up a convertible subframe from a yard.

I'm wondering if it wouldn't be too tough to knock the solid bushings out when one might come across a subframe on the ground in the junkyard.

[Gosser]

ah very interesting about the cab sub frames:


There happens to be one at my yard, I wonder how hard it is to pop the mounts out. Its probably more trouble than its worth.

[jj94tt]

You mentioned that you've done the upper strut bushings twice. Did you diagnose a failure there of some sort?

Just chasing an annoying clunk, I presume. I am doing the same.

[Kevin C]

My initial impression is that the rear front subframe bushings are not the cause, I need to get a few days of driving on it. I will say that the steering feels more responsive and the car feels tighter with no loss of ride comfort. So far there has been no downside to putting in stiffer bushings I have no idea why the softer ones were ever an option. The tighter feel on turn in entering a corner is nice and seems to make the S4 steering rack feel like it supposed to.

[jj94tt]

These bushings went up in price over the weekend from $65 to $80 a piece at ECS... that pretty much priced me out of the game.

[Charles.waite]

Just a bit of info I was looking up today (bored at work):

Subframes—
S/RS4 & B6 A4 Sport: 8E0 399 313 BG
B6/B7 A4: 8E0 399 313 BD
Bushings—
S/RS4 & B6 A4 Sport: 8D0 399 419 Q
B7 A4 Front: 8D0 399 415 D
B7 A4 Rear: 8D0 399 415 E

It appears that there are no differences between Sport and non-sport for the b7 which is odd considering the B6 sport models had the same bushings/subframe p/n as the B6/7 S4 and B7 RS4. Odd they walked back on the stiffer subframe bushings on the B7 S-Line...

Also, there are other places to buy the bushings than ECS...

https://www.audiusaparts.com/oem-par...ion-8d0399419q

[jj94tt]

Also, there are other places to buy the bushings than ECS...

Huh... I didn't think these dealer parts stores typically had free shipping. Plus, ECS pricing usually isn't that far off for OE parts. Thanks for the link... now the internal debate with my budget is back on... thanks alot. :)

[Charles.waite]

Lol, I do what I can.

[Kevin C]

Huh... I didn't think these dealer parts stores typically had free shipping. Plus, ECS pricing usually isn't that far off for OE parts. Thanks for the link... now the internal debate with my budget is back on... thanks alot. :)

https://cars245.com/en/catalog/?q=8D0399419Q It will take about 4 weeks to get them from these guy and you have to pay shipping ($38 a bushing and $24 to ship, $179 total).

[944CS]

If you think the clunk was coming from the metal part of the bushing hitting the unibody, you should insert a 1/16 piece of rubber in between to eliminate the metal/metal contact and report back. I may try this myself.

[DPDISXR4Ti]

ah very interesting about the cab sub frames: There happens to be one at my yard, I wonder how hard it is to pop the mounts out. Its probably more trouble than its worth.

Thanks for posting a pic of the factory cab sub-frame. Interesting to note that the aftermarket AL bushings are a different (simple) design whereas the factory AL bushings look a lot like the rubber bushings, but made out of AL. Are they 2 pieces like the after-market AL bushings? If yes, since the through-hole is oval, I would think you could knock them out with a big drift pin coming through the hole at an angle. Using junkyard terrorist tactics, a long ~12mm bolt could perhaps do the trick. Please report back your findings. :)

[fR3ZNO]

If I had to guess it has to do with manufacturing methods and scale. The Audi aluminum bushings are made with probably some form of die casting, etc so they have that structure to save on material usage. Whereas the aftermarket ones are machined and less concerned about material usage since they’re made in much smaller quantities.

[Charles.waite]

Oh wow. Never realized those mounts were solid metal, I didn’t zoom in and assumed those “spokes” were rubber.

I bet they do that to make the Cabbie chassis as rigid as they can since there’s no top section to box it in. I’ll poke around in VCDS in a bit and find a part number.

[fR3ZNO]

Oh wow. Never realized those mounts were solid metal, I didn’t zoom in and assumed those “spokes” were rubber.

I bet they do that to make the Cabbie chassis as rigid as they can since there’s no top section to box it in. I’ll poke around in VCDS in a bit and find a part number.

TIL VCDS is a parts lookup. I think you mean ETKA... lol

[Charles.waite]

Hah yea the other 4 letter acronym.

[Charles.waite]

So the A/S4 Cabrio 6MT subframe is P/N 8H0399315Q (the Tip one is 8H0399315T) but the bushings are specifically listed as "No replacement part". My guess is they're bonded to the subframe at the time of manufacture. Curious if they're actually removable...

[fR3ZNO]

So the A/S4 Cabrio 6MT subframe is P/N 8H0399315Q (the Tip one is 8H0399315T) but the bushings are specifically listed as "No replacement part". My guess is they're bonded to the subframe at the time of manufacture. Curious if they're actually removable...

As someone who’s looking at replacing their rotted front subframe soon, a direct swap might be easier. However, it seems like finding a 6MT Cabrio subframe is hard, all the ones on eBay I see have additional trans brackets welded to them...

As for the bushings, it looks like they should be able to be pressed out. Clicky Click

[Kevin C]

The ones you linked to look doable. From what I can tell there are two versions and one of them seems to have welded steel on one side and a cast bushing on the other. One other thing is I'm finding is that the best reason to do the swap is better overall feel.

[Charles.waite]

I mean they have to get them into the subframe somehow, so they must be removable. But I don’t think it’s something you’ll be able to get out easily with hand tools at a wrecker...

[fR3ZNO]

I suppose you could creatively engineer a puller tool with some bolts, etc. Something like the wheel bearing puller kit from Harbor Freight (or just use that if you have one). Although, I wonder if they would install easily into a subframe originally designed for rubber bushings. I've read a lot of people have issues with the fitment of the 034 bushings due to sloppy tolerances. So I wonder if the Cabrio subframes are made to different tolerances so that the aluminum bushes can be properly pressed in.

Clicky Click

Our bushings are precision CNC machined to within a few ten-thousandths of an inch, however the stock steel subframe has VERY sloppy tolerances. Due to this, it will be required to clearance your subframe to fit these bushings, a sanding roll or carbide grinding bit can be used. The amount of material varies on each subframe. Audi made these very sloppy as the stock subframe bushings have plastic sleeves, however our billet aluminum bushings require a much higher tolerance fit.