My tapping sound is getting louder

I've been hunting this damn sound for a few months now. But all of a sudden today, it stepped it up a notch. It's gone from a faint tapping noise when sometimes engine breaking, to now always audible while driving, and very very loud when engine breaking.
See (listen to) the video below. If I put my foot down on the clutch, it stops.

Now that it's this loud, I can tell that it's coming from the transmission tunnel. About 6 months ago I noticed I was starting to get some clutch rattle in idle, I wonder if this is the clutch getting really bad?

I doubt it though, I'm expecting one of you to tell me I've got a gear box or transfer box about to die? Just my luck.

Diveshaft UJ's would be my first port of call - but then it sounds like more like a bang than a tap to my ears

What have you checked already ?

Both props have been off and inspected. I replaced one despite its UJs being ok, and the other is only a year old, and was still in very good condition.

I initially thought it was a CV joint as I had a little play in one, so replaced that.

I thought it might have been the vacuum pump so replaced that.

(Obviously this is before I worked out it was coming from the vicinity of the tunnel)

The main reason I thought it might be UJ's was the frequency of the tap/bang/clunk ( whatever it is ) - To me, it seems to be more road speed dependent than engine speed dependent .... ?

Do you agree ?

What about the diff lock - is that all free and shipshape ? not half engaged and half disengaged ?

Check all your exhaust mounts are solid and none have rusted through.

I would say first port of call if drain the trans oils and see which one has silver in it!
Kind of sounds like gear teeth just rubbing or engaging to deeply, might be worth popping the pto plate off and having the gear out, that way you can check the two bearings that support the gear and the gearbox output shaft bearing for play.
Watch out as you pop the plate off as there is always half a spoon full of gear oil that is just waiting to shoot down the top of your shirt/overalls!

Disco1BFG said:

The main reason I thought it might be UJ's was the frequency of the tap/bang/clunk ( whatever it is ) - To me, it seems to be more road speed dependent than engine speed dependent .... ?

Do you agree ?

What about the diff lock - is that all free and shipshape ? not half engaged and half disengaged ?

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I don't agree no sorry. The tapping increases frequency with engine revs rather than vehicle speed. I can be moving slowly but at the top end of the range for 1st and the noise is like a woodpecker!

lynall said:

I would say first port of call if drain the trans oils and see which one has silver in it!
Kind of sounds like gear teeth just rubbing or engaging to deeply, might be worth popping the pto plate off and having the gear out, that way you can check the two bearings that support the gear and the gearbox output shaft bearing for play.
Watch out as you pop the plate off as there is always half a spoon full of gear oil that is just waiting to shoot down the top of your shirt/overalls!

Click to expand...

I drained the oils a few weeks ago, and apart from a very small number of metal particles in the gear box, not much else came out with the oils from the gear box or transfer box.

I guess I'll have to try your gear inspection idea. I've never done that before though. Are there any guides anywhere?

HeywoodFloyd said:

I don't agree no sorry. The tapping increases frequency with engine revs rather than vehicle speed.

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That's why I thought it might be the exhaust knocking. It's inextricably linked to engine revs. Sometimes it turns out to be the simple things

If it stops with the clutch dip, have you thought of a clutch release arm problem ? Silly I know, but it could be a partial fail ...

Al2O3 said:

That's why I thought it might be the exhaust knocking. It's inextricably linked to engine revs. Sometimes it turns out to be the simple things

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Just checked, all is well with the mounts, solid as a rock as far as I can tell

Dippypud said:

If it stops with the clutch dip, have you thought of a clutch release arm problem ? Silly I know, but it could be a partial fail ...

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Something in the clutch, is I think, my best hope, so I'd love it to be something like this, rather than gearbox related.

HeywoodFloyd said:

I don't agree no sorry. The tapping increases frequency with engine revs rather than vehicle speed.

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Don't be sorry - I was asking for clarification ...

Thus it has to be clutch or mounting related - what about engine mounts ? I remember a story about an MG that made a noise which could not be found .... but the steering rack was being damaged - eventually, it transpired that an engine mount had failed, and this was allowing the engine to strike the rack on the over-run ! - witness marks were only visible when everything was clean .

In terms of your clutch - would a cheapo boroscope attached to a smart phone get deep enough into the bell housing to give some more clues ?

Disco1BFG said:

Don't be sorry - I was asking for clarification ...

Thus it has to be clutch or mounting related - what about engine mounts ? I remember a story about an MG that made a noise which could not be found .... but the steering rack was being damaged - eventually, it transpired that an engine mount had failed, and this was allowing the engine to strike the rack on the over-run ! - witness marks were only visible when everything was clean .

In terms of your clutch - would a cheapo boroscope attached to a smart phone get deep enough into the bell housing to give some more clues ?

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I've got one of those thinggies somewhere. I've been considering a clutch overhaul for a while now though anyway as I drove someone else's a few month ago, and was shocked to find that the weight of an elephant wasn't required to change gears

HeywoodFloyd said:

I've got one of those thinggies somewhere. I've been considering a clutch overhaul for a while now though anyway as I drove someone else's a few month ago, and was shocked to find that the weight of an elephant wasn't required to change gears

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Might be a clue then ....

Dippypud said:

Might be a clue then ....

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But it's been like that since I bought it, 4 years ago.

HeywoodFloyd said:

But it's been like that since I bought it, 4 years ago.

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Might be why the PO sold it, wasn't tough enough ....

Right. 300Tdi (?) with which GB ? R380 ?

Heavy clutch is a good clue as to the fork being kaput - due it being eaten alive by the fulcrum ball ....due crap design and/or being fitted dry.....

does the noise go away if you ride the clutch? I.E. just put the release bearing in contact with the pressure plate ( rather than full disengage ) ? - at which point I suggest the centre of the PP is failing .....

Heavy clutch in good order is easy to fix - remote servo - I did a thread

Disco1BFG said:

Right. 300Tdi (?) with which GB ? R380 ?

Heavy clutch is a good clue as to the fork being kaput - due it being eaten alive by the fulcrum ball ....due crap design and/or being fitted dry.....

does the noise go away if you ride the clutch? I.E. just put the release bearing in contact with the pressure plate ( rather than full disengage ) ? - at which point I suggest the centre of the PP is failing .....

Heavy clutch in good order is easy to fix - remote servo - I did a thread

Click to expand...

300tdi conversation, LT77 GB.

I'll take her out for a run tomorrow to see if the noise goes away with a full disengage or less. Currently have only been trying full rather than riding it and listening.

I've seen vids about the fork before, but assumed the car would be undriveable if it had failed, rather than 4 years of a heavy clutch.

HeywoodFloyd said:

300tdi conversation, LT77 GB.

I'll take her out for a run tomorrow to see if the noise goes away with a full disengage or less. Currently have only been trying full rather than riding it and listening.

I've seen vids about the fork before, but assumed the car would be undriveable if it had failed, rather than 4 years of a heavy clutch.

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Also see if it's there when coasting, naughty I know, but it'll be drive train or not, failing that take front prop off, do same --- front on, rear off, do same ...

Narrows your list of culprits ...