Knocking

[h2o]

Hi
My 2004 Galaxy TDi suddenly started knocking  under acceleration - its not really noticeable below 30mph but gets worse as the speed increases - as in the rate of knocking increases. By 70mph its really pronounced but as soon as I lift off the accelerator it completely stops but as soon as I apply my foot to the accelerator it returns straight away. I'd be grateful if anyone could advise me as to what may be at fault. Thanks.

[Mirez]

A constant knock-knock-knock whilst going along or a single knock when you accelerate or lift off?

The former will almost certainly be a CV joint gone bad (most likely inner) whilst the latter could be the stub axle joint or the engine roll restricter.

[h2o]

Thanks for the response.
Its a constant knocking but only under acceleration, as soon as my foot comes off the accelerator it stops - would that happen if the CV joints gone?

[Chrispb]

Hello h2o and 

As said check driveshafts/cv joints.

[Mirez]

Yeah pretty much! Once you have and power "on" then the CV will be under load hence the noise. Sometimes, but not always, its possible to just re-pack it with grease

[SPIKEY]

I had the same symptoms but an accompanying wobble, it was indeed the drive shaft that had failed.
Should be easy for a mechanic to diagnose.
Parts can be found pretty reasonably with some on here using I believe polish manufactured ones, however garage labour charges will ne what adds the main bulk to the final bill

[h2o]

Thanks for all the replies / help.
I've been busy with work and haven't got round to sorting the problem yet - I took the Galaxy for a drive yesterday and for some reason the knocking seemed a lot less apparent but I'm still going to check the CV joints this evening...

However, I have just read the Common Faults section and I think I may have worn splines on the gearbox output shaft - it seldom happens, but a couple of times when I've changed gear and began to accelerate the car appears to momentarily lose drive and once I lift off and reapply the accelerator it's ok again.
Could this also be a reason for the knocking?

Many thanks.