Gearbox bearing. Fixable?

[Lawrence832]

hey people,
First question of the new year.



Video is of my cg10 engine running.

Chugging sounds dissipates when you press the clutch pedal down. Thefore gearbox idler bearing seems the most logical

New luk clutch last year and release bearing so not that

Do people agree with my diagnosis of the idler on its way out?
If so what's the treatment? Can I stuff some engine oil in the gearbox to shut it up or is that a stupid idea?

 

[frank]

sounds more like the clutch cush-drive springs to me lawrence

 

[Lawrence832]

Well it's the same clutch from when I did the engine change last September and when it was all apart I never noticed problems with the springs. Sound was happening before then

Oh and I also if it's helpful the noise dissapears when you raise the revs ove 1100ish

 

[pollyp]

when the clutch plate damper springs are sitting too loose in their housing they emit a metallic rattling noise when:
neutral gear (no torque load through spring),
clutch engaged (spinning plate),
idling below 1k rpm (not enough centrifugal force to prevent the loose springs from dropping/rattling under gravity).

rattle stops when applying torque in gear and/or rpm above 1k rpm.

could be caused by:
- springs too short,
- springs damaged/snapped,

- holes in the hub flange and clutch disc that the springs sit in were made or worn too large beyond the length of the spring,
- lip edge in the clutch disc that captures the springs are too loose.

when input shaft bearing goes:
- it constantly whines/rattles whenever the clutch is engaged & spinning the input shaft throughout the rpm range,
- whining changes pitch with rpm,
- whining get louder with amount of torque applied.

the whining is the sound of gear teeths microscopically crashing into each other (cos the shaft bearing isn't precisely held secure), and the damaged input bearing grinding itself to bits. the longer and harder it's driven with that whine, the more permanant damage there is.

if oil level has dropped for some reason (leak or human error) and it wasn't driven far with the audiable whine, fix the main cause first (repair leak or seal or slap back of head), refill oil back to spec and hopefully it'll prevent further damage.

if the bearing was damaged from excessive stress or simply worn out, replace the bearing asap to preserve the gears (checking synchros also a good idea)
https://www.micra.org.uk/threads/pollymobiles-rebuild.35251/page-120#post-706665

 

[Lawrence832]

Hang on tho guys. It was making the noise when I first fitted the 998 engine from my donor car, that would have been when I first noticed it. I remember hoping it was the clutch release bearing so when I had to change to the second 998 (had a different flywheel) and gave it a new clutch the sound was still there?

So it's had a new clutch but kept the same gearbox

Hence why I thought idler bearing

 

[Guesst4094]

The way I see it, If for some reason we have to remove the gearbox where I work we always try and do the clutch and release bearing, there would be no point changing the gearbox or getting it Repaired then putting it back on without doing the clutch, Sort of defeats the object.

 

[Lawrence832]

I agree with you guest.
That's why when I did the second engine change I fitted the different flywheel I had so I can fit a bigger friction plate, along with the rest do the clutch

I dunno. I'll buy another gearbox for when I do another engine change in the future and change it then. It seems silly to take one apart to try and fix it when I've go no experience of gearboxes

 

[Guesst4094]

What about getting one refurbished?

 

[Lawrence832]

Is it really worth it when I can buy one for £50?

 

[Guesst4094]

Brand new?

 

[frank]

i would diagnose it properly first, has yours still got the sheet metal engine/gearbox sandwich plate lawrence ?

 

[Lawrence832]

Nope I took it out. Had a choice of three different ones from my three different engines but none fitted and sealed the area off so I chose to leave it off.

Why do you ask Frank?

 

[frank]

so that you can use a listening tube mate, to pinpoint the sound

 

[Lawrence832]

That's a not bad idea. I've got an old stethoscope I modified to work like that to find the pully gone on a mates engine. When I've next got a day off ill investigate and report back

 

[frank]

i use a length of hose personally they,re very effective