[200q20v] Drive Shaft Problems

Bernie Benz b.m.benz at prodigy.net
Thu Apr 5 18:13:04 EDT 2001

Hi Peter,

Is that 1/4" play axial or radial?  I have overhauled drive shafts on
several 5KQs, but as yet not on my 200Q nor the 90Q, only because the
exhaust systems on both are almost toast and could not be removed without
total distruction.  Soon to be replaced though.

On my first 5K many years ago, I replaced the center bearing with one for a
Ford Ranger, but I expect that using the BMW bearing would be slightly
easier.  This center bearing alignment, both axial and radial, is critical
when replacing the drive shaft.  I have developed my own straight edge
alignment technique for the two plane radial adjustment of this center
bearing, thus avoiding the need for Audi's special tool.

The front CV joint is subject to much heat from the exhaust pipe, and needs
a shield.  Over time, 100K miles, the joint grease fries hard, causing joint
problems.  I've always been able to save this joint by r&r, cleaning, and
relubing.  A suitable shield is easily made, using a piece of flat sheet
metal held to, and just off of the exhaust pipe by two muffler clamps.  Add
this shield when you are working in the area.

Here is an interesting and simple procedure that I developed, not previously
disclosed, to test the relative alignment of the engine and rear end, while
the drive shaft is removed.  In doing this, I found that Audi apparently
does absolutely no such alignment, and thus relies totally on the CV joints
to mask gross missalignments.  Further, correcting this engine/rear end
missalignment really smooths out the drive train viberation, rumble and
noise under high torque loads.

Here is the rational and procedure.

Optimumly, the rotational axis of the transmission output shaft should be
congruent with the rotational axis of the rear differential input shaft.  A
basic chassis design objective, the CV joints being used only to handle
engine, tranny and rear end rubber mount dynamic deflection errors.  This
shaft alignment can be easily tested to a high degree of angular accuracy,
and not quite so easily corrected, with the drive shaft removed, as follows:

Stretch a string between the tranny and rear end CV flanges, such that it is
tangent to the OD of each flange.  To check alignment in the vertical plane,
rotate the flanges such that the string is on the bottom of the flanges in
the vertical plane through the shaft center lines.  For the horizontal
plane, the string wants to be in the plane of the horizontal shaft CLs.

Now, using a machinest's 12" blade tri-square, reference the base of the
square on the flange face and note/measure the error at the 12" end of the
blade to the string.  Do this for each flange in both the H and V planes.
Now, all you need to do is to move the engine/tranny and/or the rear end
such as to eliminate these alignment errors.

In one case, I have had to rotate the engine/tranny on its vertical axis,
and rotate the rear end on its horizontal axis to correct angular errors
that measured as much as 1/4" in the 12"!  This procedure is exactly what
one must do if one is using a rigid coupling shaft between driving and
driven machinery components.

Are we having fun yet!  Go for it!


> From: Peter Dowker <pdowker at cisco.com>
> Organization: Cisco Systems, Inc.
> Reply-To: pdowker at cisco.com
> Date: Thu, 05 Apr 2001 10:05:37 -0400
> To: Bernie Benz <b.m.benz at prodigy.net>
> Subject: Re: [200q20v] 200 20V stalling
> Hi Bernie:
> Intersting comment about the alternator - my understanding is based on several
> years of quattro list threads and my personal experience.
> Re:  the prop shaft - 1999 replaced center drive shaft bearing (and got
> $crewed
> for the entire shaft 'cause I didn't know better....) now the front drive
> shaft
> CV joint has about .25 inches play in it and is rattling under moderate
> acceleration.
> Bernie Benz wrote:
>> Peter,
>> I don't believe that these cars have a basic alternator problem.  Some may
>> have high current wire junction or connector problems, but not alternator.
>> Tell me the symptoms of your propeller shaft problems and what you have done
>> about them.  I had some on a 5KTQ and have some unique solutions.
>> Bernie
>>> From: Peter Dowker <pdowker at cisco.com>
>>> Organization: Cisco Systems, Inc.
>>> Reply-To: pdowker at cisco.com
>>> Date: Wed, 04 Apr 2001 22:03:48 -0400
>>> To: Charles Baer <charlie at istari.com>
>>> Cc: Audi 200q List <200q20v at audifans.com>
>>> Subject: [200q20v] 200 20V stalling
>>> I have the same problem myself. Based on the pulled codes from the
>>> diagnostic computer - it's a low voltage issue. These cars have a
>>> chronic problem - poor alternator design and high load from
>>> Headlights,A/C, radio etc will reproduce your symptoms on my car -
>>> usually in the rain...
>>> I believe Avi Meron has a rebuilt alternator that seems to be the ticket
>>> - as usual, no problem that : time, money, and ingenuity can't solve.
>>> --
>>> Regards,
>>> Peter Dowker
>>> 1991 200tq
>>> - still working the prop shaft bearing issues-
>>> _______________________________________________
>>> 200q20v mailing list
>>> 200q20v at audifans.com
>>> http://www.audifans.com/mailman/listinfo/200q20v
> --
> Regards,
> Peter Dowker
> Manager, Systems Engineering
> Cisco Systems, Inc.
> Empowering the Internet Generation
> +1.804.762.5556

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