Delrin drive shaft support

[Kaklikian, Gary]

Even with the delrin driveshaft center  mount, won't enough flex be retained
in the drivetrain due to the rubber motor,  transmission and rear diff
mounts?  I had a problem with failing motor & transmission mounts on my 4000
turbo ( the motor mounts  are the oil-filled variety), which was resolved by
building a very stiff front motor mount attached to a large steel plate
welded across the bumper support crossmember.  Less flex under power, no
more broken motor mounts, and no noticeable increase in body vibration.

I've also had a rear diff mount fail. And, although a new driveshaft center
bearing assembly was fitted about 15k miles ago, the drivetrain seems to
have developed excessive play which is noticeable in on/off throttle
transitions.  (Yes, I drive the car on the track frequently, with the center
diff locked, which  puts more stress on the drivetrain components than your
typical daily driver.)

So,  my concern is "Will the delrin driveshaft support minimize stress on
and movement of the motor/tranny/rear diff rubber mounts  and reduce
driveshaft wind-up and overall driveline flex without putting undue stress
on the driveshaft CV's, u-joint, etc?"  If I read your post correctly, Syl,
your answer is "yes",  but at the expense of short-term failure of the
delrin.
I'm curious Syl, when you say you've rebuilt several driveshafts, which
components have you replaced? Anyone ever have to replace the center
u-joint?
 
Also, regarding vibration transmitted to the body. I think as long as you
retain the stock rubber motor,tranny and diff mounts and the rubber
front/rear subframe bushings, vibration levels should be accepable. I know
delrin subframe bushings are available, and race cars use aluminum ones, but
I don't think either would be desirable on a street car.  

I'm definitely going to try Javad's delrin driveshaft support.

Gary Kaklikian
86 4ktq
92 S4



> ----------
> From: 	S. Jaworski[SMTP:syljay at optonline.net]
> Sent: 	Thursday, February 15, 2001 7:49 PM
> To: 	quattro at audifans.com
> Cc: 	JShadzi at aol.com
> Subject: 	Re: Delrin drive shaft support
> 
> 
> I took a look at the family album . . to see if the center bearing was
> located after the U-joint. Its located in front of the U-joint. I think
> that
> may pose a problem with a solid mounting(delrin) for the center bearing.
> 
> Here is my thinking on this:
> 
> 1. The engine moves when it produces power.
> 2. This movement is a rotation around one of the side engine mounts.
> 3. That means that the attached differential will move up and down with
> the
> torqueing.
> 4. The center driveshaft flange will move up and down, and so will the
> attached driveshaft.
> 5. The driveshaft front CV joint will also move up and down. No, the cv
> joint will not flex and "absorb" the movement since the axis of rotation
> is
> not centered on the cv joint but on the engine mount.
> 6. The drive shaft moves . . . but the after end of this drive shaft is
> locked into an immovable bearing. The solid mounting of the delrin bearing
> support will not allow movement.
> 7. Something has to give . . . the delrin plastic . . at the point where
> the
> bearing is pressed in most likely. It may not fail immediately, but with
> repeated flexing you'll end up with stress fractures . . . it's just a
> matter of time.
> 
> I guess the rubber bearing mounting has two functions . . 1. to reduce
> vibration transmittal to the car body. 2. To allow for driveshaft flexing.
> 
> Is my analysis off-base?
> 
> I've re-built two driveshafts already, and I hate parting with $180 for a
> center bearing when I may be able to put one together for much less. No,
> its
> not that I'm cheap . . . I just have an attitude problem with overpriced
> parts.     :-)
> 
> Syl
> 88 5000q
> 90 100q
> 
> ----- Original Message -----
> From: <JShadzi at aol.com>
> To: <syljay at optonline.net>; <quattro at audifans.com>
> Sent: Thursday, February 15, 2001 12:41 AM
> Subject: Re: Delrin drive shaft support
> 
> 
> >    Well, let me address your questions...first off, yes, delrin will
> introduce a slight amount of noise and vibration, but not much as I can
> attest to the prototype we did on a V8 quattro.  Infact, with the reduced
> driveshaft slop, the car actually feels smoother, especially during
> throttle
> transients.  Everyting is a compromise, use rubber and you are very
> isolated
> from vibraiton, but then you have to put up with excess deflection and
> reduced longevity, something the delrin solves in both respects.
> >   As far as the Mercedes part, it should replace the the stock rubber
> piece fine as long as the bracket is modified accordingly...I don't agree
> with epoxy, it won't last a mile IMO.  It also sounds like a lot of work
> IMO, what I am proposing will use the stock bracket, the delrin piece fits
> inside the stock hollowed out bracket-no cutting or welding, a job that
> can
> be accomplished by anyone using a drill and common hand tools.
> >    I hope I answered your questions, the decision is yours to make  =)
> > Javad
> >
> > In a message dated Wed, 14 Feb 2001 11:31:03 PM Eastern Standard Time,
> "S.
> Jaworski" <syljay at optonline.net> writes:
> >
> > << Javad,
> >
> > Let me see if I understand what you are trying to do.
> > 1. You want to replace the center bearing bracket rubber mount with a
> Delrin
> > part.
> > 2. You fasten this Delrin part to the center bearing bracket . . . using
> > nuts and bolts I assume? I assume you need to grind off the welds on the
> old
> > center bearing support?
> > 3. Then you will install a readily available bearing to the center of
> this
> > Delrin part. How will it be secured? Press fit?
> > 4. Then you will press the bearing center onto the drive shaft . . I
> assume
> > you will need to remove that dust shield off the drive shaft. Same
> procedure
> > that Blau tells you to do when you buy their center bracket?
> >
> > Is my analysis correct?
> >
> > I think that the solid mounting will introduce some obvious noise into
> the
> > passenger compartment . . no?
> > Have you actually tested this assembly in a car and checked for noise?
> >
> >
> >
>