[s-cars] Off with the drive shaft

[Mike Fitton]

Yeah, I thought about driveshaft alignment after switching to the 
aluminum front subframe mounts.  Those lower the rear of the subframe 
(and thus the transmission) by about 1cm and I haven't noticed any 
apparent adverse effects in the driveshaft department.

-Cheers!
Mike

Eric Renneisen wrote:
> 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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