Put my foot down and a Big Bang

[bobby_s3]

Hi guys,

I was driving the car enthusiastically this evening.

I was at a clear empty junction on a country road and turned off traction control. I put it in manual and floored in and then after 2 seconds heard a Big Bang.

Gearbox went stiff, vibration through steering wheel. Now when I accelerate or on gear change there is a big big knocking noise. It feels like something is vibrating like mad whilst I’m driving.

I have a 034 motorsport gearbox mount fitted, but could it be the mount?

I’m so paranoid now, will have to be recovered to Audi as I don’t want to cause any further damage.


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[bobby_s3]

I got the AA to come out and they diagnosed it as the lower gearbox mount.

They could see massive movement in the engine going from reverse to drive in my driveway.

I have got extended warranty on the car but I have the billet 034 gearbox insert on there.

Do you think I should remove this before I get it recovered to Audi?


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[desertstorm]

I would expect them to blame the failure entirely on that mod as there is a very much reduced damping effect from the bush so the instantaneous shock loadings are likely to be higher.

 

[bobby_s3]

I would expect them to blame the failure entirely on that mod as there is a very much reduced damping effect from the bush so the instantaneous shock loadings are likely to be higher.

Right so I think it’s best I take it off...


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[Arkious]

Ohh heck! First I’ve heard about that causing trouble. I fitted it to prevent the banging on the mount to be honest. Every time I changed gear on a harsh acceleration it seemed to knock back and fourth. It’s superb with it fitted.

I hope there isn’t anything damaged, but if it’s just the dogbone that’s gone then maybe it’s a good opportunity to have the full updated version fitted?

 

[bobby_s3]

Ohh heck! First I’ve heard about that causing trouble. I fitted it to prevent the banging on the mount to be honest. Every time I changed gear on a harsh acceleration it seemed to knock back and fourth. It’s superb with it fitted.

I hope there isn’t anything damaged, but if it’s just the dogbone that’s gone then maybe it’s a good opportunity to have the full updated version fitted?

Ye I was exactly the same, I have never had an issue under harsh acceleration until the other day.

Well I’m looking to remove the dog bone insert tomorrow, then get it to Audi for them to look at, as I still have the Extended warranty. I’m hoping it isn’t anything major either but won’t be able to tell until it’s on the ramp.

Have you got the link to the uprated one that 034 supply?


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[Arkious]

https://store.034motorsport.com/034...2-0-tsi-tdl-2-5l-3-2l-vr6-24v-motorsport.html

I believe it is this one mate, but would be worth checking first

 

[bobby_s3]

Right so I got underneath the car to take the insert off and this is what I found

Now I don’t know whether that is the mount insert fault

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[gokiwi64]

You've managed to snap the dogbone itself not the insert that's rather impressive.

 

[bobby_s3]

You've managed to snap the dogbone itself not the insert that's rather impressive.

I was wondering if the insert would of caused reduced dampening or something and that add to the issue before it snapped. Such a clean snap as well


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[gokiwi64]

I'm wondering if it was installed properly ?, If you look at the bottom of it where it goes through the cross member there appears to be quite a few marks on it. If it has been in contact it might have caused a weak point leading to the failure

 

[bobby_s3]

I'm wondering if it was installed properly ?, If you look at the bottom of it where it goes through the cross member there appears to be quite a few marks on it. If it has been in contact it might have caused a weak point leading to the failure

Audi were the last ones to touch the dog bone mount I think when they fitted the new bevel/transfer box. It’s been recovered to Audi now, so I’ll update you all with the outcome.


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[Arkious]

holy crap! that's a clean break if there ever was one. That's a cast part so was there any signs of porosity on it? other than that I don't think the insert could have caused that? if anything I would have thought it would have prevented the hammer action placed on it under heavy loads.

 

[Arkious]

I would have thought if it was going to break like that though, it would have been on launch from starting position, or a harsh second change.

 

[bobby_s3]

I would have thought if it was going to break like that though, it would have been on launch from starting position, or a harsh second change.

I know it is a super clean break as well. Well I had traction off, the gearbox in manual and pulling out of a junction. Jus planted the foot and after 1-2 seconds, just bang. Unless it did have a weak spot but don’t know.

I’m interested in what Audi will say about this.


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[desertstorm]

Did you remove the 034 mount or did you leave it in?. If you left it in I can guarantee you that it will be a very short conversation along the lines of the modified mount caused the failure.
Without the 034 mount in place there is a lot more flex available that would very much reduce the peak shock loads on the dogbone.
You are essentially making the one end a near solid mounting. The engine is moving up and down on the engine mounts and you may find that one of the engine mounts has an issue. The dogbone looks like it's snapped because it has contacted the subframe with a lot of force as the engine has moved up and down. Thats why it's broken where it has right above the edge of the opening in the subframe.

 

[bobby_s3]

Did you remove the 034 mount or did you leave it in?. If you left it in I can guarantee you that it will be a very short conversation along the lines of the modified mount caused the failure.
Without the 034 mount in place there is a lot more flex available that would very much reduce the peak shock loads on the dogbone.
You are essentially making the one end a near solid mounting. The engine is moving up and down on the engine mounts and you may find that one of the engine mounts has an issue. The dogbone looks like it's snapped because it has contacted the subframe with a lot of force as the engine has moved up and down. Thats why it's broken where it has right above the edge of the opening in the subframe.

Yup I removed the 034 mount before I sent it to Audi.

But how would it of contacted the subframe? Sorry if I’m being naive


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[desertstorm]

The dogbone mount limits the torsional twisting movement of the engine due to the torque reaction occuring at the wheels. So if your engine is making say 300Lb/ft of torque and the gear ratio is 10:1 that actually multiplies torque 10 times so the output of the gearbox is 3000Lb/ft, that's a lot of twisting force. And for every action there is an equal and opposite reaction . So whilst your tyres are trying to put all that twisting force to use on the tarmac as grip the dogbone is doing it's best to stop the engine from spinning in the opposite direction.
The engine is also supported at both ends by engine mounts whose job is to support the weight of the engine, and provide stability. In the same way the dogbone bushes go soft and don't work as well engine mounts allow more movement. If the road surface is poor the engine could be moving around more and it doesn't take much movement for the dogbone to contact the subframe. If it's heavily stressed and suffers an impact that could lead to failure.
I would ask them to check the engine mounts whilst it's in the shop.

 

[bobby_s3]

Quick update...

Got a call from Audi today and the RS is all fixed .

They fitted a new dog bone mount under the extended warranty I have. Plus I had an Audi S3, as a courtesy car so can’t complain!

I’ll be fitting the 034 insert again next week.


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[Arkious]

Glad it’s all fixed mate! I bet even after having the new S3 you adore the RS3 again. When mine was in for a month I got an A6, it was like driving an airliner by comparison with my RS haha

 

[bobby_s3]

Glad it’s all fixed mate! I bet even after having the new S3 you adore the RS3 again. When mine was in for a month I got an A6, it was like driving an airliner by comparison with my RS haha

Cheers mate!

It was nice having the S3 but I was loving the RS when I got back init. Nothing quite matches that 5-pot noise!

Hopefully I won’t break it this time! I need to now fit the 034 ARB like you did, just haven’t found the time!


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