btw.... i know where there are 2 more 60L 5 sp dogleg gearbox's in a scrapyard......they want 6000 baht for them... sounds like it may be a good investment/insurance to get them.

ok, been for a quick thrash around the block, no chattering noise except when decelerating in 5th gear from a high speed.
at lower speeds no chattering noise....

other than that its a bit "rough" sounding, but goes into gear nicely and operates very well..

i'm quite enqouraged that it only happens under high load so that means it may be only in the early stages....

ive only noticed it in 5th.. but then again i'm usually in 5th when i decelerate.....
i'll have a drive about and see... get back to you shortly.....

according to Clyons8 hint about clutch throwout bearing and what i read on the clutch tech wiki (and my personal mechanical intuition!) it all points to main input bearing.....

Does it happen roughly the same in all gears, or is it worse in 1 2 3 and less so in 4th?

Clutch throwout bearing

hi and thanks (to all) for taking the trouble to think about this and reply...

I drove the car to work today and did a little experimenting...

decelerate when in gear = chattering noise
press clutch when decelerating in gear = no noise
car at idle and in neutral = rough grinding noise
car at idle in neutral with clutch pressed = no noise.

i think its pretty conclusively a bearing issue... so thats me under the car again this weekend !!!

i'll let you know how it goes...

does anyone have a manual or description of how to replace the bearings ? i have seen the pictures on the tech wiki, but a cant get hold of any bigger/clearer ones...

Without seeing it in person, this is a guess (at best). As gearboxes and bearings wear, the layshaft and the mainshaft (the two basic 'axis' points of the relevant gearsets will (under load, or decel) move apart, just a little bit, perhaps a few thou or so, I don't know how much precisely (on mini gearboxes, more like 2-3mm - no kidding!) The teeth no longer mesh like they once did, and will over time wear according to that mesh/interaction pattern. And as such, they'll potentially start to whine a little. Interestingly, if you then replace the bearings, they are once again 'realigned' to where they should have been, but remember they have been wearing (however slowly and slightly) according to that 'spaced apart' extra clearance, so when you move them back into their original spacing, they can actually make more noise.

But these sort of noises are generally more like a whining noise, not a grinding or chattering noise.

THe last time I had something like that happen, one of the bearings was on teh way out, and the gears (iirc) just barely scraping on the gearbox casing. Not too long afterward, it 'broke' all the way, and 1st 2nd and 3rd didn't work at all, but I managed to get it to work in 4th (since that locks the mainshaft - input and output shaft together, no power needs to go via the laygear/shaft) to limp it home.

It sounds more like the second situation, but without actually hearing it it is pure guesswork.

Considering what those gearboxes seem to be worth, it's probably worth taking it apart sooner rather than later, where you might be able to effect repairs just by replacement of the usual 'consumable' parts that are available, rather than having to source gears or other bits which typically would require a second gearbox to source them from....

Hi, its not a "shaft hitting the car body" sort of noise, more of a metalic "chattering".

Ive never opened up a gearbox before, but i'm a mechanical engineer so not afraid to give it a go... is it easy to replace the countershaft bearing ? (i would replace all the bearings in one go if i have to go to the trouble of removing the gearbox).
is there any online guide to doing this ?
I read in the online wiki that maybe it could be an issue with the input bearing also....

very frustrating as i just got the car on the road again after 6 months of restoration work...

My guess is a bearing, maybe countershaft bearing. But I have never experienced those symptoms firsthand.

Could it be the shifter base or tailstock hitting the body of the car?

hoping someone can advise me what to do...
ive recently installed a 2nd hand 60 series dogleg 5 speed box.
it works fine in all gears but i get a 'çhopping' noise when i decelerate in gear. if i press the clutch then the noise dosent happen.
i filled the gearbox with gear oil (GL4) before installing it in the car... does anyone know what is causing the noise,.. and how can if be fixed ? i'm hoping is just a bearing .....