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Violent Vibrations when downshifting into second after installing catback

altosv6

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I recently installed a x-force 2.5 inch catback on my 2011 SV6, after finding a really good deal on gumtree. The exhaust works perfectly and sounds great until i downshift into second gear. If i dont rev-match when dropping into second, the car violently vibrations underneath me. When i had the stock exhaust it would be completely fine. I recently got a new clutch installed so i dont think it is a clutch issue. This also only occurs when i down shift into second at a mid to high rpm, at lower rpm such as under 2000 it shakes much less. It also occasionally happens at third but it is much less violent.

If anyone has any advice or knows how to fix this, it would be greatly appreciated
 

Immortality

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Was it doing it before the change of clutch?
 

Immortality

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I'd be going over everything that was touched during the exhaust install.
 

hademall

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I recently installed a x-force 2.5 inch catback on my 2011 SV6, after finding a really good deal on gumtree. The exhaust works perfectly and sounds great until i downshift into second gear. If i dont rev-match when dropping into second, the car violently vibrations underneath me. When i had the stock exhaust it would be completely fine. I recently got a new clutch installed so i dont think it is a clutch issue. This also only occurs when i down shift into second at a mid to high rpm, at lower rpm such as under 2000 it shakes much less. It also occasionally happens at third but it is much less violent.

If anyone has any advice or knows how to fix this, it would be greatly appreciated
I’m not too familiar with all things exhausts, but does an engine have to be re-tuned or something when the exhaust system has been upgraded?
 

lout

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reminds me of when i was teenager
had new dual 2" exhaust fitted to hq gts
had a bad banging noise when i gave it some stick
as if the exhaust was banging on something
turned out unis were worn
but didnt show up until i started accelerating heavy so i could hear the new exhaust
so i would be checking centre bearing rubber
 
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