help to diagnose clunking!

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steve bain

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Morning all.

So my 1.8T A3 has started to clunk. heres the run down. Couple of weeks ago lowered in 50mm ish on coilovers and it slightly clunked when cornering hard left. (like this: clunk ...clunk ...clunk, to me it sounded rotational and was a good solid clunk) I assumed it was the driveshaft fowling the arb so raised it up 5mm and it went away, mostly, but still did it a bit
to stop this clunk i have now replaced all wishbone mounts, top mounts, new coilovers obviously, new drop links. i have inner arb bushes to replace too.

heres the odd bit! there are no visible marks on anything that would show that it is being continuously hit. the arb has rubbing as on full lock it grind on the driveshaft, but that is definately a different problem.

today it was awful! last night i drove for an hour on the motorway and today it was awful.

now it clunks when turning left or going straight. it clunks when i take up drive and let it off. and it is definately rotational.

my thoughts are cv joint or the drivers as thats were noise seems to be from and lowering it has just made the problem come to the surface. not sure if inner or outer.

or that my new wheel bolts are fractionally too long and are catching. although this feel ok on the ground but the extra weight of the car may effect it. dunno. but this has all happened since lowering.

any opinions or advice appreciated. If i can't fix it this weekend it will have to go to the garage as i can't keep driving it with the noise!
 
should add also. i replaced pass side outer cv boot the other day which may have disturbed something. although the noise is on the other side as far as i can tell. also the cv boots on drivers side look in good nick.
 
thanks for your response.

problem is a can't see how they would cause a rhythmic clunking which only happens when turning left... and now straight ahead. I can try that tonight though as quick enough to try. i think it is fitting them that has highlighted another problem....
 
I see what your saying and I'm just throwing ideas in the air for you.

The clunking started when fitting the coilovers, they could have highlighted a weakness elsewhere but you have changed most of the majob suspension components except the ARBS.

Try raising them as it wont hurt ;)

I'm sure I'll start getting loads of knocking noises after I do my suspension tomorrow night but I'm not going anywhere near as low as you.
 
thats cool mate and i appreciate any advice.

alos, thats not low! on the rocco i ran out of thread! and had to raise it up as i bent the wishbones on the chassis :) oops! the beetle has less than an inch of ground clearance, the rocco just over an inch!

i think for £20 i'll buy the cv joint so i have it to replace when its in bits and i can rule it out. it is the consistant rotational clunking that is increases in timing with speed. it does seem odd that it would fail with the boot not split though. as it was rotational i thought of the arb to driveshaft but that is definately a grind rather than a clunk. is it speed related, not bumpy road related too so that rules out bushes really!

car has done 145k too so is likely to be on original cv joints.
 
Could the drive shaft be jumping splines? (big 'Ol shot in the dark)
 
never heard of that. but worth a look. i think the drivers side driveshaft may be coming off tonight to investigate! (maybe this weekend!)

also i noticed the other night that there the drivers side wheel seemed to be warmer than the pass side. could this point to anything? or is it than my tracking is out? (i want to sort all bush related issues before getting this done) and was dragging that tyre a bit.

could brakes binding cause this kind of noise?

blinking cars!!
 
just thought of more. when accelerating the noise is not so obvious. as soon as i free wheel (ie clutch down) it is really really bad!! so would drive be taking up the slack in the cv?
 
i have just had a moment i think.

if when the car is jacked up should i be able to slide the driveshaft back and forth between the wheel and tranny? i'm ****** sure i shouldn't as it should be clipped in at the outer cv end.

mine does! why did this penny not drop ****** ages ago. i guess thats it! the driveshaft is sliding around all over the shop when it shouldn't be! it should be fixed at outer cv end shouldn't it?! the amount of times i've wobbled it around.

gonna take a look at lunch and see what can be done.
 
Theres a bolt in the middle of the the brake disc, could need tightening up?
 
Theres a bolt in the middle of the the brake disc, could need tightening up?​
Click to expand...

i'll check that too although i did note that last time i looked at it the lock tab was correctly engaged as it had a brand new nut on it.

come to think of it the cv boot was replaced at xmas by previous owner to get through mot. so good chance it was run dry and joint is shot or he didn't engage shaft into joint properly and the cv boots have more or less kept it in place! and lowering it has caused the issues.

this is sooo coming to bits tonight!
​
 
no worries mate. driveshaft are easy enough to do. folks are normally put off by the odd inner cv bolts and the huge torque needed to get hub nut off. hours job tops.

gonna strip it tonight and see how i go. the more i think about it i think the pressure clip which holds the outer cv on the driveshaft has failed. Lowering the car has increased the angle inside the inner cv (strange 3 wheel device!) and is knockin on its outer lip.

Steve
 
right. problem solved. kinda.

the really bad clunking that got worse and worse i am ashamed to say was my wheel trying to fall off! i torque wrenched it up to 110Nm and it came loose! gonna keep an eye on that! i noticed that the screw to hold the disc in place was loose and was preventing the wheel from seating correctly so hopefully tat will be ok now.

this is how low it is on the coilovers

DSCN2638.jpg


DSCN2644.jpg


i replaced my inner roll bar bushes which were shot

DSCN2633.jpg


i shortened my links by 10-15mm as a complete stab in the dark which stopped the arb hitting the driveshaft. no comments about my welding please! messy and quick but does the job.

DSCN2635.jpg


DSCN2636.jpg


DSCN2646.jpg


previous rubbing!

DSCN2630.jpg


both cv feel tight but a bit dry if that makes sense. not today, but on sunday i am going to repack them with grease as they are solid still if that makes sense.

BUT i now know the problem. the driveshaft is hitting the ****** chassis rail! going to notch it this weekend, then go lower....

i am going to hunt out a TT roll bar too so it goes under the driveshafts. lowering...why do we do it!

that is all. thanks for helping an looking
 
result! outer cv was dry as a bone so rebuilt it and clunking has mostly gone. just the driveshaft hitting the chassis now!
 
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