vibration/shudder at 70 - possible alternatives (other than wheel balance?)

[rocco_crossing@hotmail.com (Rhett Farnum)]

HOw about flat spots? I have at least one tire with a flat spot on my Cut' 
and she likes to shake between 76-80mph. Just a thought.



Peace Out,
Rhett
Rocco_crossing
'83 Rocco (autocross ready, tune up, harness bar, rear wheel bearings, and 
finally I may get to makeing it look better!!)





>From: "Allyn" <amalventano@sc.rr.com>
>To: "scirocco list" <scirocco-l@scirocco.org>
>Subject: vibration/shudder at 70 - possible alternatives (other than wheel 
>balance?)
>Date: Mon, 21 Apr 2003 20:28:24 -0400
>
>ok, the rieger has had the same shudder at 70ish for the longest time.
>
>things changed:
>a-arms, bushings (all), bearings (all), half shafts (replaced with a
>questionable set), engine/tranny, engine mounts, and a totally different 
>set
>of wheels. not to mention rotors and hubs (i think this covers just about
>every moving part).
>
>...and yet i still get the shudder...
>
>exact symptoms:
>
>- 0 vibration felt in wheel, even with the shudder at its worst.
>- alignment is close enough such that it couldnt cause a problem like this
>- shudder is not constant, the vibration is consistent with wheel rotation
>at 70 mph, but it comes/goes at a 1 second cycle (kinda like its amplitude
>modulated).
>- shudder seems proportional to throttle application. the other day i did
>several runs on the highway, coasting from 90-60 in neutral, and the 
>shudder
>seemed to go away. shudder returns when holding speed at 70, and gets worse
>under acceleration.
>- feels like an out of balance wheel, but i've also felt the same feeling
>when i had a bad inner cv (however the bad inner cv had a constant
>vibration).
>- also seems like bad inner cv in that its almost a side-to-side vibration,
>felt in the floor under the center console.
>
>possibilities:
>1. other set of half shafts (rebuilds from potterman) had the exact same
>problem with the inner cv.
>2. frame/engine is misaligned such that one of the half shafts is at its
>compressed limit when installed / car on ground. possibly forcing tranny
>over as it rotates, causing the vibration.
>3. both sets of wheels/tires have had the exact same imbalance, after being
>balanced several times between both sets (doubtfull).
>
>suggestions???
>
>(thx in advance for info)
>Al
>
>
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