Re: Driveline alignment

[David Rubie <drubie@domain.elided>]

Mike Grace wrote:
>I've been chasing down a drive line vibration problem for about a year now,
>and with help from Tom Sahines, I think I may have stumbled onto something.
>It seems that my drive line donut is under tension created by the drive
>line center bearing mount and the motor/transmission mounts. Tom suggests
>that the resulting distortion of the donut ~6mm must be eliminated via shim
>washers on the donut bolts or other means and I'm hoping that this will
>solve my vibration. Before dropping the drive line again to extract the
>donut (it's a pain with no lift and only two arms), I loosened the motor
>mounts at the cross member and the tranny support cross member and pushed
>the motor as far rearward as it will go (this bought maybe 1mm). Then, as I
>dreaded removing the donut again to add shims, I started wondering how the
>experts out there deal with the general problem of aligning the motor and
>drive line after a rebuild (assuming all new motor/tranny mounts), since
>there is some slop in the mounting points and since it does seem to be
>fairly critical to get things lined up and happy. What sequence have others
>used? Has anybody else dealt with this particular problem before?

I've dropped my Alfetta tailshaft more times this year than sanity suggests is wise
(chasing an oil leak among other nasty things) and the thing always
bolts up correctly first time, everytime.  Unless this car is unique
(doubtful), my guess is that somebody has fitted the wrong centre
bearing or some other horrible  thing has visited upon your car
(i.e. wrong engine mounts, poorly repaired engine mount sheet metal
or something).  This car didn't vibrate even when chunks were missing from
all three donuts though, so I'm beginning to suspect I'm one of those
people who just don't notice the vibration.

The other thing that might be wrong is that you are missing the spacer washers
for your rear engine mount - they are about 6mm tall and can bend the drivetrain
out of shape.

dave.

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