please help needed

[tatty0001]

hi, newbie here. need some help if anyone can.

bought a 1.8 gti (agn) a couple of months ago.

I have a loud deafning noise that comes on strong at 3900 rpm and seems to go at 4100rpm. this has only happened since a garage put a new centre silencer on it when i was working away, took it back and they cant find anything wrong with it then had to come back home and have had 2 more garages look at it one of which ats and they say theres nothing wrong with it.
ats said it could be backbox cos there is a slight rattle but not much.

it was fine before the new silencer and rear discs n pads.

its as if its vibrating somewhere because if the centre of the car vibrates quickly when i hit 3900rpm.

just wondered if anybody could give me tips on what to look for.

cheers

[archie837]

what kind of noise is it?

Could be a wheel bearing starting to rumble, but you;re saying it's rattling from the centre?

[rio_gti]

exhaust mount/bracket/rubber

[tatty0001]

all the exhaust mounts were changed when he done the silencer.
its not a wheel bearing noise it tends to boom at 3900rpm. its loud tho it rattles my dash.

it couldnt be the backbox could it??

surely if it had went wouldnt it be loud all the time??

[rio_gti]

exactly and the centre one the exhaust sits on it make sure it isnt wedged its hard to explain but mine was clamped onto it with a jubelee clip when it was vibrating like mad but as soon as the clip came off it stopped (as it was able to move) so it stpooed after that

[tatty0001]

i will give it a check in 10 mins n get back to u

[tatty0001]

just had a good check now and there was a heat shield that was loose but nothing else all brackets were ok.
took it out for a spin and maybe i think it could be the backbox is gone.

when i used to have cars with perfomance exhausts they used to boom at certain revs too.

[turbokid23]

i dont understand how the back box can effect the dash?? u have a good reason now to get a catbk system 

[tatty0001]

i didnt think that too but it must be because it does seem quite loud, its definatly nothing with the brackets or anything i was pullin each of them for an hr tonight.