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Gearchange 'Clonk'

Tony,

You remember very well - I do indeed have an amp back there! However the noise is certainly associated with the changing of gear rather than things in the car; there is no noise when going over bumps, potholes or sleeping policemen and it sounds very mechanical.

I think that getting less stressed about it is pretty good advice. I'm seeing a very knowledgeable friend next Saturday and will value his opinion but the local Porsche specialist had a drive and a listen and didn't seem to think that there was anything much to lose sleep over.

Thanks for your help.


Oli.
 
Wondered if it was rocking rather than bouncing, but then you would also notice it when braking - unless you have shouty brake pads!

 
I don't think it is rocking - as you say, it would happen at other times. The brake pads are stock and the brakes aren't noisy so they aren't hiding anything.

It really feels like it's selector noise, but I don't even know if this is possible!


Oli.
 
Update to this (if anyone is interested ... ) it turned out to be the near side outer CV joint. Four of the bolts were snapped. Yes, snapped. And the other two weren't tight. All quite worrying. And the symptoms don't make entire sense; I don't know why the noise was heard when changing gear rather than when pressing or releasing the clutch. However I am confident I have got to the bottom of it and I've cobbled it back together with three replacement bolts of a slightly different pattern, which should get me through the next week or so.

Thankfully I managed to get three of the broken bits of bolt out of the hub. Unfortunately the last one eluded me and I'll have to take the hub off to tackle it, which is damned annoying. I guess it'll end up being a wheel bearing replacement at the same time as it seems that the bearing doesn't often survive this particular exercise so I guess I need to mug up on how to replace rear wheel bearings.

Thanks for your input and help - particularly 944Scott for the pictures.


Oli.
 
Oli,
It does make sense that it you heard it when changing gear as the driveshaft/CV is not feeling the torque from the engine during the gearchange. So it's all being held tight whilst in gear then gets a momentary relief during the gear change before the torque slams back in again as the clutch bites again. That switching on and off of the torque through the driveshaft and CV joint is whats making your loose CV joint clonk.
 
Good advice from your specialist then....

Although it doesn't quite explain the amount of play you described?
 
Tom, Yes, that explanation makes sense but I'd expect the torque going through the joint (and hence clamping force keeping it quiet) to ease up when the clutch is pressed in, not when the gear is changed. This is the part that I really can't explain, other than to say that the car now drives as I'd expect it to (quietly and smoothly).

Ed, yes, I'm not that impressed by the specialist - although in fairness it did sound very much like the noise was only being made when the gear was being changed. Mind you I'd expect him as a specialist to know more about things than I do and hence to spot idiosyncrasies like this.

The lash could be partially explained by movement at the CV joint end. Or by my inexperience of what to expect in terms of gearbox lash.

Thanks again for your help. I'm glad to have an explanation and to have it semi-solved. I'll be happier when I have the hub off and the broken bit removed and six new bolts in there but it works for now.


Oli.
 
A happier outcome than another gearbox of unknown history, though most of them from the breakers are low mileage..... I've read the CV bolts are supposed to be replaced whenever they're removed, I bet most aren't though.
 
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