[DeTomaso] Oscillating vibration

[Tomas Gunnarsson]

Mike,

Are your half-shaft-halves installed in phase?

Tomas

----- Original Message ----- 
From: "Mike Thomas" <mbefthomas at comcast.net>
To: <Detomaso at realbig.com>
Sent: Sunday, August 26, 2007 6:30 PM
Subject: [DeTomaso] Oscillating vibration


>I have about 200 miles on my new motor, and am in the debug phase of the
> project.  I've had an interesting issue pop up and wanted to post it to see
> if there is anything I am not considering as a potential solution.
> 
> When I get up to about 75-80 in fifth gear (2500-3000 rpms), I get an
> unusual oscillating vibration.  I've certainly felt alignment or wheel
> balance vibrations before in other cars, but never of an oscillating nature
> that rose and fell at a constant speed/rpm.  I am pretty sure it is chassis
> related as hanging in the same rev band in lower gears does not induce it.
> I checked the tightness on all 16 half-shaft bolts, and they are snug.
> Next, I am going to have the wheels balanced tomorrow.  If that does not
> cure it, I am going to have the balance checked on my new half-shafts.
> Other than that, I know both rear rotors are slightly out of true, dragging
> a bit at one point when I spin the wheel while it's off the ground, so I'm
> wondering if the drag on the brakes at that particular speed sets up a
> harmonic between the two rear wheels to create the oscillating effect, but
> that would suggest the wheels were of a different diameter and rotating
> different speeds.  I had the alignment recently done and no changes to the
> suspension or bumps hit to knock it out, but I guess that could be something
> else to check.
> 
> Any thoughts from you guys would be appreciated.
> Thanks
> Mike Thomas
> Panteras Northwest.
> 
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