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Transmission Whine


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#1 clipper

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Posted 12 September 2018 - 07:35 AM

Hi all!

 

My long suffering C8 has developed a new "issue" and, ahead of taking it in to see the doctor I can't help but wonder what it might be.

 

At first we noticed a ever louder whining noise, which seems to come from the transmission, and linked to engine speed (downshifting makes the revs rise, the pitch of the whine rise and increase in volume). The noise is now very noticeable on the over-run / under engine braking.

Now I have noticed that at idle in neutral, there is a similar, but less intrusive noise. I'm pretty sure that it is the same issue but without load. The noise goes away upon depressing the clutch pedal.

 

At first I suspected the clutch release bearing, but a noise from this wouldn't go away on pressing the clutch right? On the contrary, it is when it would be more noticeable?

 

Therefore, I am suspecting a gearbox bearing on the input side. Any known issues like this?

 

The car had a new clutch about 2 years / 50k kms ago, and it now has approx 210k kms.

  


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#2 paul.h

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Posted 12 September 2018 - 01:20 PM

If it is the clutch release bearing then if you lightly press the clutch pedal at idle to the biting point and not all the way down, the noise ought to go away or change.

 

At the mileage though I would suspect gearbox bearing wear. I have replaced Saab gearbox bearings at around 150k miles when worn. The whining noise tends to be greater under load as you accelerate. On one the wear was that bad it would jump out of gear. Only way to see which ones are worn is to take the gearbox apart but if you are having to pay somebody then it is going to cost a lot less to fit another used gearbox. Once in bits you can get the bearing numbers off them so they can be bought at a bearing shop.

 

You should check the gearbox oil level - this is not a maintenance item other than just a look for any leaks. If you are not planning on keeping the car for many years it is possible you could live with it. On one of the Saabs I tried this but it got to the point it jumped out of gear frequently and as well as the bearings I also had to replace one of the gears.



#3 clipper

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Posted 12 September 2018 - 04:51 PM

Thanks. I'll pay more attention next time I drive it and see exactly what clutch action affects the noise.

 

I'm certainly planning the "live with it" solution for the time being, but as you say, things could get catastrophic quite quickly... that said, I have a 32 yr old BMW with a layshaft bearing rattle that's been there for 10 years. That gearbox has 360k on it and still going.

 

Obviously I'm not expecting a C8 box to last that long, but it would be nice to know if this is the beginning of the end, or if we can eek another two years out of it.


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#4 clipper

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Posted 17 September 2018 - 01:39 PM

In neutral, pressing the clutch partially down (to where the biting point would be if it were in gear) does make the noise go away, without having to depress the pedal to the floor..

 

In a very quiet garage, I can hear the output side of the clutch spin up when the clutch plates meet on biting point and the noise kicks in at that point, it is directly related to the clutch on the gearbox side or to the gearbox input shaft. 

 

I'll take it to the mechanic this week to get the box oil checked.


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#5 paul.h

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Posted 18 September 2018 - 02:14 PM

Citroen tend not to have gearbox oil level plugs, instead the oil is drained out and the correct amount is put back in. If you have it drained you could have a look for tiny specks of metal worn off the bearings.



#6 clipper

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Posted Yesterday, 11:12 AM

I'm still hoping that it is the thrust bearing really, although I'm not sure if that is a good thing to be hoping for as I have no idea of the replacement cost.


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