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Discussion Starter #1
Hi guys,
Sorry that my first post is searching to answers to a problem, but sometimes French ownership is like that:nono:

I have a 407 Zenith 2.0 DW10TED4 16v HDI.

The past couple of days i have developed an interesting problem, which i fear may be the gearbox.

The symptoms are as follows:
Between 46-50MPH i have a whining noise.
This will happen in any gear, so at any revs, but only at this speed.

This led me to believe it was more of a wheel bearing issue for example BUT when you dip the clutch, the noise goes away. So it definitely has something to do with the drivetrain.

The only thing that has got me stumped is that it happens at the same speed, but in any gear so at any revs- but only in the speed range i mentioned above. However it must be box or engine related as it goes as soon as the clutch is dipped.

Apart from that, the car still drives as well as the day i got it. I just have developed this odd noise!
 

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It sounds like a worn differential. Diffs may become worn at the speed at which the car is usually driven and a wear pattern is created in the diff. (Don't try this at home, but the theory says that if the noise happens at speed "x"mph, then it will happen at 2x also) One test is to get the noise sounding on a flat road and then take your foot off the accelerator – the noise should go because the pressure has been taken off the crownwheel/pinion teeth but you say that it goes when you put the clutch in… that has the same effect.

If this is the case, a rebuild/replacement is the only cure – a thicker oil will not help. Word is that you’re looking at about £1,000. Make a judgement, how bad is it? If it is not too bad, the gearbox could outlast the car. If you have a warranty, the next step is to try and persuade the garage that the diff's gone and you want a replacement.

Less likely is the turbo or a sympathetic vibration, i.e. some part vibrating at a certain engine / gearbox revs – this can be tested when the car is stationary and taking the engine to those revs at which the noise usually occurs.
 

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Discussion Starter #3
PureJoe said:
It sounds like a worn differential. Diffs may become worn at the speed at which the car is usually driven and a wear pattern is created in the diff. (Don't try this at home, but the theory says that if the noise happens at speed "x"mph, then it will happen at 2x also) One test is to get the noise sounding on a flat road and then take your foot off the accelerator – the noise should go because the pressure has been taken off the crownwheel/pinion teeth but you say that it goes when you put the clutch in… that has the same effect.

If this is the case, a rebuild/replacement is the only cure – a thicker oil will not help. Word is that you’re looking at about £1,000. Make a judgement, how bad is it? If it is not too bad, the gearbox could outlast the car. If you have a warranty, the next step is to try and persuade the garage that the diff's gone and you want a replacement.

Less likely is the turbo or a sympathetic vibration, i.e. some part vibrating at a certain engine / gearbox revs – this can be tested when the car is stationary and taking the engine to those revs at which the noise usually occurs.
It does exactly as you say, so i would say it is a worn diff:(
It isn't too bad at all, as in you cant hear it with the stereo on and only with all music/fans off.

I will try and call the warranty company tomorrow but i fear they may say it is only wear and tear and not 'broken' as the car still functions as it should bar the noise. However i will try and get it inspected. You never know they may say yes.

I don't believe it is too bad at the moment so i think it will be ok, or im hoping so. I only have 2 months remaining on the current warranty so i may leave it for a few weeks, see if it develops and if not, just make sure i renew the warranty to cover me for it failing in the future.
 
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