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Discussion Starter #1
Hi all,

as im now slowly working through the more serious problems in my new car, i've now come to address my rear end knock. Basically if put the car in second accelerate up to 3000rpm, then take my foot off, i get a loud "clonk" from the back of the car (or atleast i think it is the rear, hard to tell). it does it in all gears, but most noticeable in lower gers as it pulls through them quicker. Another way to get the sound is if i change gear and allow the revs to drop to low when i come off the clutch. ie so the engine is being pulled up to the road speed rather than the revs coming down.. if that makes sense...

not too sure what would cause this? no clonks or vibration when normal driving, and its not suspension related as doesn't knock at all over bumps. i was thinking it could be the bushes that hold the diff in place, allowing it to move around a bit when there is a sudden change in speed of drive-train?

any thoughts appreciated :thumbsup
 

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It could be that your subframe has torn away from its mounts, its a commonly known problem with the e46, but you would definitely be better off getting a garage to diagnose it. as it could be something as simple as the bushes being completely knackered or even the drive shafts.
 

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or diff mountings (bi*ch of a job to DIY) - doing these sorted my rear end knock when going on and off the gas...
 

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Discussion Starter #5
Thanks chaps, i'll take a look under when i get a chance to get in the air. would have thought if the subframe had torn i would get knocks all the time, not just on lifting off and drive-train jerks?

have read horror story's of diff mountings.. do most jobs diy, but if its that might take it to a garage... will play in these be obvious once i get under and have a poke about?
 

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2001 e46 330d - rear end knock

Just look for cracks in the metal were the subframe mount is, think ur model was built with a strengthened subframe though
 

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I`ve got the same problem mate.Two garages have been unable to diagnose the cause, and told me to "just leave it to get worse" !!
 

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Try letting the clutch up and down sharply in reverse and then in 1st, see if you can replicate the noise, could well be diff bushes. Not uncommon.
 

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Discussion Starter #10
yeah, ive noticed the noise when quickly going from 1st to reverse aswell. would this be caused by the jolt of the drive-shaft suddenly changing direction? can anyone recommend a decent garage in dorset that wont rip me off, and give me a ball park cost figure, if it does turn out to be diff bushes?
 

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I had a clunk coming from the mid-rear of my 330d. I was working on the car at the weekend, checked the prop shaft and the prop shaft flex-disc (guibo) was in a bad way.

I have a video here

https://docs.google.com/leaf?id=0B3...DktZDQwOTM4NzQxZGNm&hl=en_GB&authkey=CMSM5P8E

I Replaced it with a part from GSF for £44 - BMW wanted £120 and had to order in :shifty: As much as I like using OEM parts, I thought this was way overpriced.

Not a difficult job to do. I had the exhaust off so access to the prop shaft was good, I'm not sure you can change the flex disc with the exhaust still on but maybe someone with more knowledge can answer that...
 

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Discussion Starter #13
Just got under the car for the first time, at a glance the guibo looked in good condition, however if a grab it it has about 5mm movement in all directions :eek. suspect this might be my clunk! any ideas what a garage would charge to do this?
 

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Just got under the car for the first time, at a glance the guibo looked in good condition, however if a grab it it has about 5mm movement in all directions :eek. suspect this might be my clunk! any ideas what a garage would charge to do this?
5mm radial movement on the propshaft/guibo is normal. :thumbsup It's just the slight freeplay/backlash between the gearbox and rear diff. Non adjustable either for you.
 

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Discussion Starter #15
ah ok, didn't realize that was normal! which is kinda good, but also not so good as i guess that makes it more likely its the diff bushes..
 
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