Clutch knocking noise

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Hugo
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#41 Re: Clutch knocking noise

Post by Hugo » Thu Oct 19, 2017 1:45 pm

zigzagsky wrote: I'm 95% certain it does vary with engine speed and I can hear it when driving in 1st gear but need to listen carefully to see if it occurs in all gears.
See if it is constant or varies with the amount of power applied and/or over-run. Also check that it varies with engine speed rather than road speed (in other words, that the speed changes when you change gear).
Hugo Miller - rebuilding an imported Series II OTS & converting to RHD

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#42 Re: Clutch knocking noise

Post by zigzagsky » Fri Oct 20, 2017 1:15 pm

So with huge thanks to Pat and his well equipped garage, I think that the problem has been identified and, as suspected by Hugo and Christophe, it is indeed the gearbox and not the clutch.

Getting the car up on a 2 post lift and using a borescope camera, we could see nothing amiss within the bell housing.

However we did notice during a road test that the knocking does occur when being driven with the clutch pedal depressed i.e. coasting. Although the noise is loudest around the front of the bell housing, it emanates from the gearbox.

Not really the news I wanted to hear but it is what it is.

Looks like I have a bit of a winter project ahead as I think it would be 'good for the soul' to have a go at removing the drivetrain myself. I can also take the opportunity to sort out the engine bay whilst the gearbox is away being reconditioned and refurbished.
Brian
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#43 Re: Clutch knocking noise

Post by Hugo » Fri Oct 20, 2017 1:30 pm

zigzagsky wrote: However we did notice during a road test that the knocking does occur when being driven with the clutch pedal depressed i.e. coasting. Although the noise is loudest around the front of the bell housing, it emanates from the gearbox.
Hmmmm. Next question - when you coast with the clutch depressed, does the knock drop in speed to match the engine, or does it stay the same to match road speed? And what happens when you knock it into neutral while moving? Does the knock stay the same speed or slow down? Or does it disappear?
I still cannot imagine what this might be or how it was caused - just fishing for clues.
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#44 Re: Clutch knocking noise

Post by zigzagsky » Fri Oct 20, 2017 1:50 pm

Stays related to road speed when coasting.

Not tried putting her in neutral... yet.
Brian
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#45 Re: Clutch knocking noise

Post by Hugo » Fri Oct 20, 2017 3:11 pm

If it's at road speed, that rules out the pressure plate & release mechanism. So why is the noise coming from the bell housing?
If the speed of the knock decreases when you knock it into neutral, that points to the input shaft or layshaft, or possibly one of the mainshaft gears. If it stays the same, that points to just the output shaft or speedo drive. But then it shouldn't be coming from the front.
If the Fates are smiling on you, you might just be able to see something if you take the top cover off the gearbox. But it would help if we had an idea what we were looking for - that neutral test above might give us a clue.
You could also try knocking it into neutral & killing the engine & coasting - from what you have said so far, it probably won't make any difference, but I'm still clutching at straws to be honest.
And what happens when you go on & off the throttle while driving? Does that make a difference?
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#46 Re: Clutch knocking noise

Post by Series1 Stu » Fri Oct 20, 2017 6:06 pm

The bell housing could be acting like a, well, like a bell, and amplifying the sound from the gearbox.

Also consider the input shaft spigot bush in the end of the crankshaft.

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Stuart

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#47 Re: Clutch knocking noise

Post by Hugo » Fri Oct 20, 2017 7:26 pm

Series1 Stu wrote: Also consider the input shaft spigot bush in the end of the crankshaft.
Regards
No, wrong way round! The noise STOPS when he depresses the clutch ;)
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#48 Re: Clutch knocking noise

Post by Series1 Stu » Fri Oct 20, 2017 9:41 pm

Hugo wrote: No, wrong way round! The noise STOPS when he depresses the clutch ;)
That's not what he said.

I'll go back to minding my own business!
Stuart

If you can't make it work, make it complicated!

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#49 Re: Clutch knocking noise

Post by E600 » Fri Oct 20, 2017 10:32 pm

With the car on the lift and running the noise is coming from the box. Using the scope the flywheel, clutch cover, release bearing and inside of the bell housing are unmarked. Given the noise I would have expected to see swarf or gouges on the bell housing, but all appeared unmarked.

Regardless of whether it's box or bell housing the work involved is broadly similar, engine and box out for further inspection, and given the noise I wouldn't be driving it far.

I would suggest oil drain, checking the magnetic sump plug from the box and a look at the oil, I wouldn't be suprised to find a missing tooth!

Next as suggested top of the box off for a visual, but again this results in a box out fix.

Best of luck with your first major E Type strip and if stuck give me a shout.

Regards
Pat

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#50 Re: Clutch knocking noise

Post by Hugo » Sat Oct 21, 2017 2:16 am

I've had a brainwave - does this gearbox have a sleeve over the input shaft that the release bearing slides along? I have know these break off. Unlikely, but less unlikely than anything else I can think of.
I didn't have my brain switched on earlier when I suggested it might be the output shaft, since the noise is present when stationary.
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#51 Re: Clutch knocking noise

Post by Hugo » Sat Oct 21, 2017 2:18 am

Series1 Stu wrote:
Hugo wrote: No, wrong way round! The noise STOPS when he depresses the clutch ;)
That's not what he said.

I'll go back to minding my own business!
Sorry, that is EXACTLY what he said, in his very first post; "there is a knocking noise now coming from the bell housing which generally goes away when the clutch is depressed."
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#52 Re: Clutch knocking noise

Post by mgcjag » Sat Oct 21, 2017 8:57 am

Hugo..Stuarts post above was a good addition to the discussion...there was no need to shout him down.....you are not always correct.....in post 42 Brian says " However we did notice during a road test that the knocking does occur when being driven with the clutch pedal depressed i.e. coasting. Although the noise is loudest around the front of the bell housing, it emanates from the gearbox."
Steve
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#53 Re: Clutch knocking noise

Post by E600 » Sat Oct 21, 2017 9:47 am

Hugo wrote:I've had a brainwave - does this gearbox have a sleeve over the input shaft that the release bearing slides along? I have know these break off. Unlikely, but less unlikely than anything else I can think of.
I didn't have my brain switched on earlier when I suggested it might be the output shaft, since the noise is present when stationary.
There's no sleeve on the first motion shaft.

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#54 Re: Clutch knocking noise

Post by Hugo » Sat Oct 21, 2017 1:33 pm

E600 wrote: There's no sleeve on the first motion shaft.
Damn! Back to the drawing board I guess ;)
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#55 Re: Clutch knocking noise

Post by Hugo » Sat Oct 21, 2017 1:54 pm

mgcjag wrote:Hugo..Stuarts post above was a good addition to the discussion...there was no need to shout him down.....you are not always correct.....in post 42 Brian says " However we did notice during a road test that the knocking does occur when being driven with the clutch pedal depressed i.e. coasting. Although the noise is loudest around the front of the bell housing, it emanates from the gearbox."
I wasn't "shouting him down", merely disagreeing with him.
I know Mr Zigzaksky has issued contradictory information to begin with, but then he clarified it in #35 with this;

"As mentioned before, depressing the clutch makes the sound disappear. Last night I tried depressing it slowly. About halfway down, the knocking stopped but when it did, it slowed briefly slightly just before - like a rotating part which stops under inertia once the driving force is removed."
Then in #44 he expanded on your quote above from #42 by stating that the noise varied by road speed, which tends to rule out the spigot bearing.
It's easy to get confused when the information comes in fragments over a number of days, as it must with something like this.
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#56 Re: Clutch knocking noise

Post by Series1 Stu » Sat Oct 21, 2017 3:48 pm

I see. And you're never the one that's confused?

You certainly confuse everybody else!
Stuart

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#57 Re: Clutch knocking noise

Post by Hugo » Sat Oct 21, 2017 9:32 pm

I am indeed confused - but I'm not the one supplying the information, only trying my best to make sense of it. If it's any consolation, I am now completely stumped. It's certainly a weird one. I can't wait to find out the answer - if we ever do - I have a horrible feeling that our friend Mr Zigzagsky will strip the whole damn thing down and still not find the source of it. I sincerely hope, for his sake, that I am wrong though.
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#58 Re: Clutch knocking noise

Post by PeterCrespin » Sun Oct 22, 2017 10:02 am

The front UJ and flange bolts are all good I suppose? They make strange noises under on/off and load reversal sometimes.
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#59 Re: Clutch knocking noise

Post by christopher storey » Sun Oct 22, 2017 10:35 am

I did wonder about that, Peter, but I think it is eliminated by the fact that the noise also occurs when the car is stationary ( see Pat/E600's posts ) and by implication in neutral

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#60 Re: Clutch knocking noise

Post by Hugo » Sun Oct 22, 2017 1:02 pm

There has been a bit of contradictory input from poor Mr Z, but I think we have established that the noise is present when the car is stationary in neutral, and slows down & stops as the clutch is depressed. The only things that do that are the gearbox input shaft, layshaft & the three mainshaft gears, plus of course the clutch centre plate.
I have no real clue how any of those items can cause such a noise however, unless something has fallen in there & taken a tooth off, which itself is unlikely verging on the impossible.
I'm out of ideas.
Hugo Miller - rebuilding an imported Series II OTS & converting to RHD

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