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

[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?

[kaanage]

For a short period, a fully threaded bolt of the same quality as the OE one would be OK - fatigue failure is a long term issue for most parts (a lot of cars would never have this bolt removed in their lifetime), unless the part was critically optimised in the first place and I'd lay long odd that this one isn't.

Why not just wrap the shank of the OE bolt with some sheet metal?

[Eddy]

Hoyhoy.

Sorry folks I only just spotted this thread, Greg the threaded shank bolts were the replacement part from VW, plus I did add some sleeving on
the little bit of blank shank left, on top of that there is added material as to where it goes in (thickness & minumun diameter)(zero freeplay).
Info a lot of VW bolts are of 12.2 tensile grade, normal hi-tensile = 8.8.

[sambb]

so eddy, did you just ask for replacement LCA front bush bolts and they just gave you different ones to the original fitment, or did you have to specify that you wanted ones with a different shank? I've just ordered replacements from VW so wondering if I need to cancel the order in favour of slightly different bolts.

thanks
sam

[Eddy]

Hoyhoy.

I just went for replacements, so I would say that you will get the same as me, which took two weeks.

[Eddy]

Hoyhoy.

Folks have a read for two post of this shortcut...To Improve Me Polo. - Page 7

I had only a little bit of slop in the torque link, now she's much better & much smoother with take-off.
Ya have to think of all the forces acting against this one & only mount fighting to keep the whole engine in place, any free play will be felt.
It did remind me of the old Cooper S days, they were a sad case in this area.

[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.

[sambb]

Well I've done my LCA's with superpro rear and front bushes ( fronts have new VW bolts with full length thread and new tighter inner bush sleeves machined up to fit them with zero freeplay). Couldn't be happier with the result for the handling. I still have stock springs and couldn't notice any adverse change to harshness at all, yet it turns in and points so accurately now and has even more of that euro planted feel - super happy. Its a generally quieter front end now with less creaks etc
HOWEVER.. the clunking is still there and I'm now convinced that its inner driveshaft freeplay. When I had it apart for the LCA job, physically the freeplay didn't feel like that much but when you twist the driveshaft back and forth it generates a really audible clunking and I'm pretty sure is the same sound I'm getting when I drive. I just can't believe how loud it is - it 'sounds' like a real problem although I'm sure it will be fine.

My car had its driveshaft inner boots replaced before I bought it. Is there anything simple they might have buggered up that could be contributing to the sound, is this something thats inherent with these gearboxes/shafts or is mine an odd one out?

[pologti18t]

I had a similar noise... that got worse in warm weather.
After reading all these posts I lubed the rollbar bushes and droplinks.... and I also lubed (silicon spray) the hinges and strikers of bother front doors.

Result... noise gone. Was it the bushes OR the door hinges