[s-cars] Off with the drive shaft

[Mike Fitton]

Yeah, what he said...

And on that note...anybody ever consider replacing the two-piece shaft 
with a once piece carbon fiber shaft?  My friend's 97 A4 has a factory 
CF shaft (believe that was a 97 thing they did), but I can't remember 
how many pieces...probably two.  But it seems to me that a CV joint at 
either end of a single shaft would do just fine and eliminate all this 
U-joint/bearing nonsense in the center.  I think custom CF shafts run 
around $1k.

Discuss.

Still workin on that carbon-kevlar weave naca-ducted bellypan...

-Cheers!
Mike

Kurt Deschler wrote:
> 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
>>     
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