[Fot] Gt6/spit diff question

[Scott Janzen]

perhaps it moved the alignment in the right direction.  All I can tell you is that the difference in the angles in my car is beyond the limit of what the driveshaft experts recommend, and making a few adjustments (trans tail mount height, etc) reduced the vibration - yes, i've had the driveshaft balanced by a good shop. 1/2 an inch relative to the distance from the front to rear mounts works out to over 2 degrees, and Spicer recommends not more than three degrees total deflection as optimum for u-joint wear and not more than 1 degree difference between the front and rear.  Not to say it won't work at greater angles, but it all makes a difference.

On Dec 29, 2011, at 6:52 PM, Rocky Entriken wrote:

My offset bushings move the hole, what? Half an inch?

They've been in my car some 40-odd years now! Originally when it was a street car, now as a race car. Never had any vibration issue with them. (Speed traps at Road America caught me at 100-plus at the Runoffs last September, no vibration).

In fact, some 20 years ago we re-mounted the diff even higher by making new mounting holes in the frame to push it up as high as space allowed, maybe another inch. Still no issues.

That's what U-joints are for.  :-)  The change in the angle is minimal, and the change at the front of the diff is zero because the front mountings are in the same place.

At least, that's my experience with them.

--Rocky



----- Original Message ----- From: "Scott Janzen" <sjanzen at me.com>
To: "Christopher Bock" <SeaCubeCo at aol.com>
Cc: "FoTTriumph" <fot at autox.team.net>
Sent: Wednesday, December 28, 2011 10:50 PM
Subject: Re: [Fot] Gt6/spit diff question


> you might want to check driveshaft angles before you offset bushings to change the height and angle of the diff.
> If this increases the differential between the driveshaft/u-joint angles front to rear, it will result in more vibration at high speeds, which I've found to be an issue with at my car at speeds above 100-110. Ideally the diff and trans are at the same angle to the driveshaft, and/or their axes are parallel.  They're not the same in my car, but I've tried to manipulate mountings to get them as close as possible with a resulting decrease in vibration.
> 
> On Dec 28, 2011, at 6:02 PM, Christopher Bock wrote:
> 
> Are the rubber bushings at the back end of the diff where it mounts to the
> frame upright replaced for racing? If so by what? Rubber? Aluminum?
> 
> Thanks
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