Shot pilot bushing is a good possibility. Another often overlooked place
is the fit of the driveshaft yoke in the rear transmission bushing.
Either one can be isolated, the pilot bush vibration is related to
engine speed, will show up at a particular engine rpm, no matter what
gear you're in. The driveshaft yoke fit is road speed related. Will
show up at only a given road speed, regardless of engine rpm.
Paul
PAsgeirsson@juno.com
On Thu, 24 Sep 1998 13:46:43 -0700 shk <shk@qnet.com> writes:
>I posted a couple of months ago about vibration I had in my '63
>Sprite.
>It has a 948 with a ribcase. The vibration is strongest around 3K
>RPM. Several people suggested I replace my U-joints which I did
>but unfortunately it didn't help. I've had an opportunity to
>road test the car some since then and I have discovered some things
>of note. You can really feel the vibration through the shift lever.
>Most curious though is if you "bump" the clutch slightly so that the
>disc slips a little you can make the vibration go away. If you keep
>doing this you can cause the vibration to fade in and out. As if some
>harmonic vibration is passing in and out of phase. The RPM range
>which
>leads to the vibration is very localized, about 400 RPM. I am not
>certain about 1st or 2nd, but the vibration is there in both 3rd and
>4th gear. I am thinking this may be caused by the pilot bearing or
>maybe bearings on the transmission input shaft. Or maybe even a bent
>shaft. I suppose another possibility would be the clutch. Anybody
>tackled a similar problem, or have any suggestions?
>
>Shawn
>
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