The dreaded driveline vibrations

[Jaap Bouma <j.h.bouma@domain.elided>]

Hi everybody,

I've just changed the twin-disc clutch on my GTV6 for a complete Milano/75
single-disc unit (excellent price at EB Spares, UK). I thought I did
everything right to prevent driveline balance problems by buying the
complete unit, but the first test drive showed vibrations around 2800rpm.
Much bad language ensued.
The thing is, I don't understand where the vibrations might come from. I
marked the driveshaft and clutch shaft yoke, numbered the bolts and put
everything back in exactly as and where it was. I am assuming that the
clutch unit (ricambi originale) was properly balanced at the factory. The
only thing I can think of is that I somehow damaged the three-pronged yoke
on the clutch shaft, but this strikes me as unlikely.
My dealer suggested putting hose clamps around the driveshaft as makeshift
balance weights. This helped, indicating that the problem is somewhere near
the clutch, but the vibrations have not disappeared completely.
What could cause this problem? Has anybody had similar experiences? If so,
did you find the source of the problem? In short: HELP!

Any input will be deeply appreciated.


Best, Jaap Bouma (Netherlands)
'87 GTV6 2.5 Grand Prix

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