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Hi,
I am new to this forum and I have a 1987 Alfa 75 twin spark. I was wondering if someone has experienced the problem I am going to describe and can give me a clue.
When I release the clutch pedal to engage clutch, even if on idle and neutral, I can feel a clonk coming from the clutch zone. In recent time I have done the following:
New gearbox supports (2 lateral ones and rear one)
Overhauled Gearbox
Brand New OEM clutch
New driveshaft guibos and centre bearing (and rebalanced shaft).
Now the car is very firm, but I could not eliminate the clonk (it was there also before changing/overhauling the above mentioned things), so I was wondering if there is something worn on the rear part of the driveshaft that might be the cause of the clonk. On the internet I could see that this affects many cars and is the result of some backlash that is suddenly taken up during sudden torsional impacts. But where would you suggest to locate the backlash if almost everything is new?
Thank you very much for your attention
Ciao
Oscar
ITALY

Oscar based on your description it sounds like it could be the bushing at the front of the dedion triangle - where it attaches to the rear crossmember.(see photo).you can usually confirm this by using a prybar and wiggling the dedion tube where it sits inside the crossmember.

Murray,
thank you very much for your reply. The De Dion centre support bushing is new as well (no more than 4000km). What I find strange is that the noise is done also in neutral at 900 RPM, when torque is very low ...
I press clutch pedal, then I release it and clonk... no problems during driving or vibrations or anything else. Just that annoying clonk.
It is just like if there was something loose and free to rotate a little bit and when I engage the clutch the backlash is taken up suddenly.
I did not change on the rear driveshaft joint the Ball, Spherical Seat, Retaining Ring, Rubber Cup and Seal (I am listing the parts of the rear joint that can be seen on the factory manual, group 15, page 9 and can be downloaded from Craig's excellent website: http://www.users.on.net/~craigf/ ). Could any of these parts produce the clonk if loose or broken?
Thank you again for your attention
regards
Oscar

Could be a bad guibo....or

"free play" in the tranny...probably in the differential...

or bad constant velocity joint..

that's about it (unless you have something loose in the trunk...or exhaust clearance issues)