[DeTomaso] Oscillating vibration

[Tomas Gunnarsson]

The U-joints must be in phase. That means that the "forks" must line up between the ends. Or if you look at the shaft from its end and imagine the end plates removed it must look like a "+" with the two ends lining up. Does that make sense?

Tomas

----- Original Message ----- 
From: "Charles Engles" <cengles at cox.net>
To: "Tomas Gunnarsson" <guson at home.se>
Cc: <detomaso at realbig.com>
Sent: Sunday, August 26, 2007 9:48 PM
Subject: Re: [DeTomaso] Oscillating vibration


> Dear Tomas,
> 
> 
>              "Half-shafts in phase"......?     I recall hearing of this in 
> the past, but I can't remember what the heck it is.   Could you refresh my 
> failing memory?
> 
> 
>                        Warmest regards, Chuck Engles
> 
> 
> 
> ----- Original Message ----- 
> From: "Tomas Gunnarsson" <guson at home.se>
> To: <Detomaso at realbig.com>
> Sent: Sunday, August 26, 2007 12:42 PM
> Subject: Re: [DeTomaso] Oscillating vibration
> 
> 
>> 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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