[s-cars] Off with the drive shaft

[Kurt Deschler]

The reason that the propshaft alignment is not so critical is that the
quattro driveshaft has CV joints on both ends that can compensate for
the driveshaft's axial movements created by the the U-joint. On a simple
driveshaft with 2 U-joints, the U-joints must be phased correctly and
set at identical but opposite angles so that the axial motion is exactly
opposite on both sides.

 	-Kurt

> ------------------------------
>
> Message: 6
> Date: Sat, 24 Mar 2007 19:58:09 -0400
> From: "Eric Renneisen" <racingiron at comcast.net>
> Subject: Re: [s-cars] Off with the drive shaft
> To: "'Mark Turczyn'" <mkturczyn at verizon.net>,	"'bill mahoney'"
> 	<airbil at gmail.com>,	"'Audi S Car List'" <s-car-list at audifans.com>
> Message-ID: <000201c76e70$49864fc0$0301a8c0 at renhoek>
> Content-Type: text/plain;	charset="us-ascii"
>
> Mark Turczyn wrote:
>> Thanks to Bill and other list members who posted me off
>> list-- I will be pulling my drive shaft off with confidence
>> soon--
>
> Welcome to the club.  I've lost count of the number of propshaft R&Rs
> I've done in pursuit of my (still) ongoing vibration problem, not to
> mention the two tranny swaps.
>
> I've come to the conclusion that you needn't be nearly as anal about
> propshaft alignment as Herr Bentley would suggest.  I know of at least
> one S4 that ran just fine after reinstall with the original shims on the
> wrong side of the bracket (therefore not shimming at all) and alignment
> calibrated with a mere pair of eyeballs (and a second pair for
> redundancy).  Upon recognition and correction of the shim problem (many
> miles later), she rides just as fine as before.
>
> Think about all the old tranny, motor, and subframe mounts in these
> cars.  The sag of those things surely tweak the propshaft alignment over
> the years, but no one ever seems to require a re-alignment with new
> shims.  Likewise, installing some of the stiffer aftermarket mounts and
> bushings would seem to tweak alignment as well, but how many people even
> think about the propshaft after the install?  Seems to be a pretty
> tolerant design.
>
>> Too bad I cannot just drop it down from the tranny in the
>> front and try to re-grease or remove it in place.
>>
>> I cannot seem to pull it back far enough for the center
>> shaft to clear the lip of the tranny prop shaft.
>
> That's my experience, too, though I suppose it's tough to say all cars
> will have the exact same tolerances here.  On mine, I have to completely
> detach the center support bearing as well as the small crossmember brace
> (four bolts) beneath the rear section of the 'shaft.  Then, you can bend
> the u-joint enough downwards (the rear half of the shaft resting on the
> still installed rear section of exhaust) for the front CV to clear the
> flange (upwards) and then it'll come down on the passenger side of the
> tunnel.  YMMV.
>
> On mine, both front and rear were kinda dry and got repacked.  That was
> no help for my vibration problem, though.  Nor was swapping out with a
> known good propshaft.  I can definitively say that my problem is NOT the
> propshaft.  Nor the transmission...
>
>>> While your at it you could check for what is one of my latest problems
>
>>> too, which could probably cause some driveline vibration.  That is the
>
>>> two bushings that attach the forward subframe cross member to the
>>> differential. Now may be a good time to change these if they appear
>>> worn.  Problem is I have no advice on how to tell if they are worn.
> My
>>> own is obvious because of the occasional metal to metal noise upon
>>> acceleration / deacceleration.
>>
>> Now you got me thinking about more fixes.   I suspected a
>> dry CV joint since I was getting a metal to metal hammering
>> when accelerating.  Now you say even with good CV joints you
>> get the same noise.
>
> I had a bad bushing here, too.  The left side one was completely torn.
> The resulting movement was easily diagnosed with simple arm pressure at
> the connection point.  I suspect the metal to metal noise described here
> is similar to what I had--a single "clunk" during drastic driveline
> transitions (such as a spirited shift).  New bushings fixed the clunk,
> but not the vibes.  If you're talking about a constant metal on metal
> noise, your bushings would have to be really bad to cause it.
>
> HTH,
>
> Eric R.
> '86 urq
> '93 urS