Fw: Delrin drive shaft support

[S. Jaworski]

> ----- Original Message -----
> From: Kaklikian, Gary <Gary.Kaklikian at compaq.com>
> To: <quattro at audifans.com>; 'S. Jaworski' <syljay at optonline.net>
> Cc: <JShadzi at aol.com>
> Sent: Friday, February 16, 2001 2:19 PM
> Subject: RE: Delrin drive shaft support
>
>
> > 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 think you misunderstand the problem. The Delrin center bearing mount
 does not restrain flex in the engine, trans, etc. The part is just too
small
 to restrain anything. The problem as I see it is that the engine and all
 associated components will stress the Delrin support . . .. and not the
 other way around as you describe it. The dog wags the tail, as opposed to
 the tail wagging the dog.

> > 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.
 *****As I stated above, the delrin support minimizes nothing. Its just
there
 to support the center of the drive shaft. But, since this delrin support is
 immobile(has no flex) as opposed to the original part which is rubber and
 flexes, any movement of the shaft in up/down or side/side direction will
 result in stress at the Delrin support as it has NO FLEX in it.

 To demonstrate what is happening: secure the tip of a long pencil in a set
of pliers. Then move the eraser end with the other hand. Easy to move it,
no? The pliers are the Delrin support, the other hand is the engine. No
matter how hard you grip the tip with the pliers and try to keep it
immobile, your other hand has no trouble moving that pencil up and down. In
the car, that Delrin support is rigidly fixed to the chassis . . it cannot
move. The bearing in this support cannot move either. Yet the drive shaft
will move up and down or sideways a bit due to engine torque. Something has
to give, and it wont be the driveshaft . . it will be the Delrin support
because it cannot flex to accomodate the drive shaft movements.

> > 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?
 ****On the 90 100q, I had a vibration which I thought was due to a worn out
 bearing in the driveshaft. I took it apart and replaced the center bearing
 with a Blau replacement. There was nothing wrong with the original bearing
.
 . .maybe just a little play in it.
 I took apart the U-joint. The U-joint insides looked fine . . no wear. So I
 cleaned the parts, packed them in grease, and reassembled the U-joint.
 I took apart the CV joints at each end of the driveshaft and cleaned them.
 Repacked them in new cv joint lubricant and installed new boots. I also
 replaced the end gaskets as they are inexpensive. I cleaned out and checked
 the grease nipple for proper operation.
 After I re-assembled the drive shaft, I adjusted the grease nipple so it
 could be accessed with a grease gun. The original mounting is square to the
 center line of the driveshaft and cannot be reached with a grease gun. I
 added grease until I saw grease coming out of all the U-joint boots . . all
 four of them. Wipe off the excess grease.
 Install the drive shaft.

 To align the drive shaft, use a string. Tie one end of the string to front
 cv joint, the other end to rear cv joint. Make it snug. The string will lie
 along the drive shaft.

 Make some "guages". Get a wood square molding, 1"X1". Cut off 3 pieces
about
an 1.5" long. Place the three pieces next to each other on a flat surface
and make sure the tops are all even with each other. If not, grab all three
pieces together as one unit, flip them and sand other side till all are
even. Now you have 3 identical measurement blocks.

Slip one block under string at the front cv joint. Slip second block under
string at rear cv joint. Use the third block as feeler guage under the
string at the center support.
Adjust center support up or down till that third block just kisses the
string.
Do the same for side to side alignment.

This is a lot simpler and cheaper than trying to make/use the alignment tool
that the Bentley shows. And if you use a smooth string, you can set the
driveshaft straight to + - .020"   . . . . good enough for me.


> > 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
  **** I've been talking to Jarad about this. I'll forward to you our
emails.
 I think that our conclusion is that the engine will torque rotate about its
crankshaft/transmission output shaft. Therefore there should be none or very
little lateral(up/down or side/side) motion in the forward end of the
driveshaft. That being the case, there is no stress imparted to the rigid
Delrin support at the center of the driveshaft.

I'm forwarding to you my chats with Jarad regarding this topic.

Oh, by the way, the vibration problem on the 90 100Q turned out to be a bad
rear wheel bearing.
And, the problem on the 88 5kq turned out to be seperated treads on one
tire.
SH_T!    SH_T!    SH_T!!!!!!!

Ahh, what the heck, I did all the work myself. Just had to pay for the
parts. Parts were pretty inexpensive . . I get them at a good discount from
a small local shop that specializes in Audi and VW parts.

It was a "learning" experience. Have to do something to get away from the
wife. Neither car talks back. I hope the wife dont read this, otherwise I'm
in a world of hurt.

Syl