Clunk when transitioning to engine driving and engine braking (on/off throttle)

[vwthunder]

- unless you're being particularly aggressive (no mechanical sympathy) on the track, you're not too likely to break new components so I wouldn't be too worried about that aspect.

But I don't know your driving style

I guess anything can fail, maybe just unlucky

[noone]

I'd get that in writing. If they change it and the issue is not resolved, I'd want some paperwork for an 'engineering' refund.

They're supposed to be the experts, shoudn't have to pay excessively for them to diagnose, I'd also ask for their hourly rate. if its more than a few hours, I'd ask for a report as I cant imagine what they did with the time.

[sambb]

sorry - I'd started a new thread on this same problem as what Kaanage had experienced until I dug this one out of the achive.

I too have this knocking when the engine is ever so slightly loaded/unloaded with the throttle at low rpm.

To test whether the front wheel bearing preload stretch nut has loosened (it may have since both inner driveshaft boots were done on the car the year before I bought it) I plan on tightening it slightly and then seeing if the knocking goes away. If it does i'll order new stretch nuts but I'm unsure how to do the preloading. I'm ok with the castellated nut/cotter pin method but that requires you to take up the tension and then back off from there to a running postion. But I'm unsure if this is the way to go with a stretch nut which by definition shouldn't be backed off from its final position as this voids its ability to hold a certain torque setting doesn't it? Or are they fitted with a torque wrench setting?

So how do I go about finding the correct pre load considering also that the original bearings ( 6yo 28k km) will likely remain in the car?

thanks for any help
sam

[kaanage]

Actually, the hub replacement didn't quite eliminate the noise - it did reduce it to just a 4th and 5th gear issue at low rpm (see Misdiagnosis by dealer - what next? for more details). There may have been a slight amount of stretch on the hub nuts but it could also have been the bolts holding on the control arms (I had the SEAT Cupra rear bushes installed at the same time).

The noise finally went away after I installed some subframe sleeves that Eddy had made up a while ago (I bought the last set).

Sorry for not updating this thread properly back in the day but it died with the tangent discussion about lightweight clutch replacements and I didn't think anyone was still interested in the original issue. I will see if I can get the torque for the hub nuts for you.

edit
BTW sambb, your inbox is full so I couldn't reply to your PM on this so I'd check the bolts for the front control arms and subframe as they seem more likely culprits to me, now.

[sambb]

righto, thanks for getting back to me on the forum. It really is a chorus of noises in front of me now. Even though everything looks to be ok its going to cop a complete re bush after I check the front hub nuts. If that doesn't do it i'll order a new set of subframe stretch bolts.
thanks
sam

[Polo GTEye N9]

Hi Sambb, a PM to Eddy would be wise.

Eddy has done lots of work and sorted thru the front subframe, LCA etc etc on our Polos. Eddy also found that the LCA front bolt was 1.5mm smaller than the sleeve it goes into to. So he brought new bolts with thread all the way along the bolt, result- no more movement slack!

I am sorting my front end out prior to fitting new front & rear suspension and bushes etc. cheers Al

[kaanage]

Eddy also found that the LCA front bolt was 1.5mm smaller than the sleeve it goes into to. So he brought new bolts with thread all the way along the bolt, result- no more movement slack!

Hmmm. I have to disagree with Eddy on this one - there are sound engineering reasons for the VW arrangement with the LCA front bolt. The thinner shaft ensures that the maximum stress is in this area rather than at the thread roots which GREATLY enhances the fatigue life of the bolt. With the full length thread the bolt will fail earlier since the thread roots are stress raisers.

It would be much better to add a polyureathane sleeve (fitted via a spiral slot if it's too stiff for a lengthwise slot)

The subframe sleeves I mentioned before are a great idea, though

[sambb]

So the standard bolts only have thread where its needed but this undersizes the shaft along the pivot. hmm thanks for that. I have access to a whole variety of high tensile bolts at work to at least try out temporarily on the front LCA bushes to eliminate that. High tensiles will be strong enough/safe won't they? VW don't have any super metallurgy going on with simple bush cross bolts do they, other than the potential issue that kaanage raised?

[sambb]

Well I just picked up my VW LCA front bush bolts and they are the full length thread type that Eddy got. All I can say is that even with the full threaded version where the shank is larger outside diameter than the original fitment ones, the amount of free play within my superpro bush sleeves is ridiculous! Can definitely see how this could cause front end noises.

But from a performance point of view I couldn't agree with you more Eddy. You can wiggle the bush nearly through a degree on the bolt - each side that'd be nearly 2 degrees total which would be a hell of a lot of toe mm change under braking like eddy said. If you didn't have really stiff rear LCA bushes I reckon the wishbone would be squirming around all over the place. I haven't done this with the original VW bush though - maybe the superpro sleeve is larger I.D than the VW one - can't say yet.

I'm going to see about getting a new inner sleeve spun up for the bushes, to tighten up the tolerances to the VW full thread bolt. When I finally put it all back together the LCA will be fully superpro'd so if the clunking continues then it ain't the bushes!!

sam

[Eddy]

Hoyhoy.

CLUNKING NOISES, folks I have to say even with everything nice & tight I still have noises, may be I have things too tight, but with front spring ratings of 350lb & now going to 425lb, you do expect some noises, old age helps with this.
But the steering is a lot better, even with -3% camber she's steer's a lot better than ever.(toe alignment is a big thing also)
Also have to reconfirm my statement from post No-53 in this thread, zero free play in the torque link = much better.