Knocking noise
Turbo Mini Forums

Driving my car it developed a knocking noise when the clutch was engaged. Depressing the pedal and the noise would go.

So I stripped it down and found the primary gear bush was non existant. So replaced that, and thought I may aswell replace the gearbox at the same time as it's been jumping out of 1st. It had a new idler gear at the same time. Re-used the bell housing, flywheel assembly etc. Checked over the engine, and everything is good and within tollerance.

Clutch release bearing is good, flywheel assembly stripped and good.


So rebuilt it, it's still knocking but not as bad as before.


It's a 1380 low spec engine, that will be turbo'd when funds allow.

1st motion shaft bearing is around 2000 miles old, and appears fine. I don't know how to check the transfer gear bearings as you obviously can't wiggle them with the transfer gear housing on.


Any ideas what could be knocking? Or help checking?

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Idler gear end float should be checked before the engine and gearbox are assembled. Bolt the transfer housing onto the gearbox with the new gasket you are going to use with the idler gear installed, and then check the idler gear endfloat is within tollerence. If its to large a clearance, you need to fit thicker thrust washers. Common problem that often gets overlooked. You can check the idler gear end float with the engine assembled, but you need to remove the primaray gear and its seal, then set up a DTi on the visable part of the idler gear, but it is far easier to do this with the engine off the gearbox.

Primarly gear end float should also be within tollerence.

When you fitted a new idler gear, did you fit new bearings? if its A+ gearbox, make sure you are using the Torrington bearings.

Also, an uneven idle caused by poor tune or ligfht weight flywheels will cause the idler gear to chatter.

Edited by Sprocket on 25th Jul, 2010.

Thanks a lot for that, no I did not fit new bearings with the new idler, I will check the idler end float today. I will order a new set now, The primary gear was spot on.

The idle is very smooth and even at the moment, as im using a standard cam waiting on my 266.

Thanks
Ben

Edited by mini_mad69 on 25th Jul, 2010.

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is it a verto? i looked at one a few years back with the same simptoms and the bolts holding the flywheel/clutch together had come loose

yeah it's verto, flywheel assembly was fine, was dissmantled checked and then rebuilt. There does seem to be a lot of end float on the idler, so will get my old man to get a dti from work. Everything else seems fine, so im assuming it's this. I suppose some new bearings couldn't hurt either.

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0.010" was the end float on the idler, using some new thrust washers It's now 0.005" which is within tolerance acording to haynes. But it wasn't wildly out of tolerance, so im not sure that was making the knock, my father now thinks it may be the flywheel not sitting true on the crank as the tail isn't amazing. So will bolt that up and check that that's true tomorrow, any other ideas?


Thanks
Ben

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Everything appears to be within tolerance and in good condition.






Heres a video of the noise, im unsure as to what it could be now.

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Just to mention, the noise goes when pressing the clutch down.

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If the noise goes when you press the clutch pedal, it "usually" means the noise is from the drop gears or gearbox input (primary motion and layshaft) as these should stop turning once the clutch pedal is down.

But sometimes, especially if the clutch is out of adjustment or badly setup, they don't stop turning. To be sure, press the clutch pedal and select any gear - that guarantees the shafts stop turning.

The other possibility is that there is something loose on the release bearing or clutch itself that stops moving once the release bearing is pressurised.

Schrödinger's cat - so which one am I ???