Layshaft noise

[one eyed mick]

It happens to many boxes in many cars and can be real pain in the -r-e it is caused by uneven /inconsistent idle speed ,highly tuned engine suffer the most and some just cannot be cured even by rebuilding the box and clutch surely a car like an r400/500 spends little time idling so there are only 4 courses to take 1 don't let it idle 2 depess clutch while its idling 3 switch the bl--dy thing off!! 4 Ignore it !!

[Paul Holywood]

one eyed mick said:

It happens to many boxes in many cars and can be real pain in the -r-e it is caused by uneven /inconsistent idle speed ,highly tuned engine suffer the most and some just cannot be cured even by rebuilding the box and clutch surely a car like an r400/500 spends little time idling so there are only 4 courses to take 1 don't let it idle 2 depess clutch while its idling 3 switch the bl--dy thing off!! 4 Ignore it !!

Interestingly I'm looking at a previous poster who mentioned lightened flywheel, that would then indeed contribute to this noise, am I right in saying a heavier flywheel would make for smoother idle speed? But obviously have detrimental affect on engine response etc..
Hence why the lesser tuned engines may not suffer the same .

Note, this thread makes for good learning.

Edited by Paul Holywood on Sunday 21st December 12:07

[rubystone]

When I sold my 6 speed HPC, the buyer questioned the CRB noise and insisted on an independent view on it. It turned out to be a problem with one of the layshafts and I had the 'box rebuilt by R & R. So you never know...the CRB was always noisy on my KR500 and I didn't ever bother to do anything about it.

[Red Seven]

Paul Holywood said:

am I right in saying a heavier flywheel would make for smoother idle speed? But obviously have detrimental affect on engine response etc..
Hence why the lesser tuned engines may not suffer the same .

Yes!
Wilder cams tend to lead to a more uneven tickover, which will exaggerate the effect of the quoted "The first motion shaft and laygear are dancing around a bit due to the fact that they are effectively idling with alternating accelerative and deccelerative cycles in time with the engine".
Using a light flywheel with a standard clutch will exaggerate this even more, and an ultralight flywheel and a smaller clutch exaggerates it even more.

Ignore any of the comments about the clutch release bearing. It's the gearbox rattling, not the release bearing.

When the clutch is depressed, the gearbox input shaft (1st motion shaft) stops (or, more accurately, slows down, and it's motion becomes damped by the oil in the gearbox), so the noise is vastly reduced.