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Guys,

Which component is making the rattling sound? Clutch disc? Doesn't make a difference if the clutch pedal is pressed or released. This makes me think it's the clutch and not the gearbox.

http://www.youtube.com/watch?v=ItR8o-RpUnI

It's sort of hard to hear on the video, but it sounds to me like it's the driveshaft rattling due to a loose pinch bolt. Then again, I sort of always default to that since it's easy and fast to check. If not it pretty much has to be in the clutch housing because with the clutch disengaged (pedal down) the input shaft doesn't really turn fast enough to make noise.

Greg Gordon,
www.hiperformancestore.com

Hi Greg,

I don't have the driveshaft with pinch bolt. I'm going to talk to RJR about his balanced and lightened rear flywheel and clutch. The clutch which is currently in there is about 6 years old.....bought from APE (obviously the real age is unknown since it came from APE)

Well, that sort of shoots a hole in my theory!

Greg Gordon,
www.hiperformancestore.com

In gear with clutch down? Same noise?

Yup.

That rules out the gearbox then.
At what rpm does it stop?

Seems to be inconsistent. Sometimes it makes noise at around idle. Sometimes around 3000 rpm. Not to sure when it stops as the car is pretty loud. I think it's the disc/spring in the disc. The throwout bearing is new.

Zeefa,

My money is on worn splines of the clutch input shaft and the rear donut spider.

Drop the rear tailshaft. Remove the spider from the input shaft. If it rattles, it will come off just with your hands. Use a solvent cleaner to fully clean all the input shaft splines and the splines inside the spider. Apply a generous amount of an anaerobic thread locking solution to both parts and re-assemble in reverse order. Do not start or run vehicle for 24 hours.

Check for rattles.

Warning. Once you do this, you will need a puller to remove the spider next time. !

If you drop the gearbox down measure the clutch shaft diameter where it goes into doughnut. If to much play there it rattles even though its for location. I think its 22mm. Some times when mechanics remove the clutch from housing they damage end of shaft from bashing it(bad mechanics). This distorts it. Rear doughnut also just wears.

My mechanic said the source is the driveshaft. Specifically the end spherical bearing (the ball and spherical seat as per the workshop manual) on the rear (probably worn or broken). Because the noise is random and regardless of clutch or gear position.

What do you guys think?

The question now is, where can I get those bearings?

It's very common to develop a rattle in the clutch input shaft splines as I have described above for you. It is also true that the clutch input spigot (locator) wears as well like Kevin has advised and I agree with. So right there you can have a compound problem of worn splines and location. The swivel bearing inside the donut may also be worn so there is a third element in the one cluster.

You will find this out when you strip it down.

The swivel bearing on the end of the prop shaft is an original Alfa part only in Oz and it should be available (albeit rare).

The cure then is:-

A new swivel bearing.
A new rear donut.
New clutch input shaft.
New spider flange.

If that doesn't fix it, your problem is elswehere. The last two items may not be necessary if you chemically lock them together as I advised before.

If you have gone that far, you may as well install a new clutch and be sure you have the flywheel and clutch BALANCED before installation.

...oh the joys of transaxles...

Yes, looks like I'm going to bring down the whole driveshaft, the 2 spherical bearings on the center and front, replace all 3 guibos, a new lightened flywheel, and unsprung clutch (was told that it WILL be streetable). The center bearing and throwout/release clutch bearing are both pretty new so I will re-use them.

...and I will check the SPLINES

Yup, but I will just use some sort of loctite for it if indeed it is the case the splines are lose.