Propellor shaft woes

[Kaklikian, Gary]

I too have a driveshaft tale (apologies for the length):

The driveshaft on my 4000tq was in good condition, the center carrier
bearing/support assesmbly having been replaced about 25k miles ago.  But,
since I'm interested in getting the best performance out of the car possible
and it does have over twice the horsepower of stock, I thought the delrin
center support would be a great upgrade.  Additionally, the center diff was
quite worn, due to high mileage and driving with it locked on the track
frequently.  So, the plan was to install the delrin center support as well
as thenew tranny I got last year from Robert Braunschweig and a new clutch.

As a first step, the driveshaft was removed and the delrin center support
with new bearing installed. The CV's at either end and the u-joint were fine
and full of grease.  On the first test drive, I noticed a 
odd noise when shifting under load and a slight vibration through the seat
at part throttle operation between 50-80mph.  Given the nature of the car, I
have a high tolerance for noise, vibration, etc, and these were definitely
minor and acceptable.  Plus,  power transfer seemed more positive (less
driveline slack) when accelerating hard and the drivetrain was smooth above
80mph. At this point, I was satisfied with the delrin support.

Next, in my constant but often misguided quest for improvement, I decided to
have the driveshaft balanced when installing the new tranny and clutch. Only
one driveline shop in the whole Denver-Colorado Springs area claimed they
could do this.  So, for $52 I had the driveshaft balanced and straightened
(the latter was done at the shop's initiative).. 

My intial test drive with the balanced driveshaft and new tranny and clutch
was terrible. The driveline vibration from before was magnified immensely
and was speed sensitive, so that above 60mph the car was nearly undriveable.
So, I removed the driveshaft and took it back to the shop. The technician
mounted it to his balancer with clamps holding the CV's at either end and
the center support mounted firmly.  The driveshaft was nearly 50 grams out
of balance on either end and 34 grams out in the center!  Then he rotated
the driveshaft on his balancer and it was only a few grams out throughout.
So, he said I need to rotate the driveshaft mounting on the car until it
reaches this optimal setting. Well, this is bs!   I've seen Audi driveshafts
removed (including mine) a hundred times, and the position of the CV's on
the tranny/rear diff is immaterial. Yes, you have to mark the two halves if
the u-joint is removed, but otherwise it shouldn't matter.

The driveline shop tech had no better explanation and claimed he'd never
seen anything lilke this (duh, it's an Audi, although BMW uses similar
setups).  Although he offered to send the driveshaft out of town to another
shop, I was pressed for time, and said the hell with it, remove the weights
you added, so now the driveshaft is back to the original factory weights
only (and refund my money).

The next test drive revealed the same part throttle vibration between
50-80mph as earlier, but again much worse and totally unacceptable. The seat
felt like one of those massage beds they used to put in motels. It did
smooth out some above 80mph, but I try not to drive 90mph in 50mph zones,
and there's too much traffic to drive full throttle very often.

So, since I had to get the car ready for the track and had other things to
work on, I said the hell with this driveshaft, got a used one from a
junkyard with the CV's and center carrier in good condition, and cleaned and
regreased it. Voila - the drivetrain was as smooth as before this whole
fiasco! I do notice some vibration through the accelerator pedal at the part
throttle 50-80mph, which has always existed,  but none of this is
transmitted through the body. Evidently, the delrin support was magnifying
this greatly. What the driveline shop did to the driveshaft I can only
imagine!

Moral of this story -- Don't f#$% with your driveshaft unless the center
support or a CV's has failed. The delrin support might work in most
situations, even though it's likely to introduce a slight amount of
vibration.  The drivetrain on my S4 is silky smooth compared to the 4000, so
it's likely the delrin support would work fine.

btw - we fitted a pump and cooler for the tranny fluid, especially for
situations when the center diff is locked.

Gary Kaklikian
86 4ktq 
92 S4


> ----------
> From: 	Peter Berrevoets[SMTP:pjberr at home.com]
> Sent: 	Thursday, May 24, 2001 7:04 AM
> To: 	1 Quattro List (E-mail)
> Cc: 	JShadzi at aol. com (E-mail)
> Subject: 	Propellor shaft woes
> 
> Having had the oppportunity to obtain a new centre bushing from Javad and
> an
> SKF bearing, I took the time do do the centre bearing re+re.
> 
> To my serious displeasure I discovered that the cv joints at both ends
> where
> so badly worn, thaat they were causing the ringing sound that I assumed
> was
> coming from my sagging centre bushing. Having access to another propshaft
> with cvs' in good condition, I swapped the cvs and fitted the new bearing
> and bushing.
> 
> Herein lies my nightmare. No amount of messing with the shaft alignment or
> balancing of the shaft has had much effect on a vibration that makes the
> car
> almost undriveable over 90 kph.  I'm getting ready to bite the bullet and
> buy a new shaft or hopefully find a good used one.
> 
> Looking for any advice from the list on relatively local (Southern Ontario
> Canada or Upper New York State - I am flexible beyond that but closer is
> preferred =( ) sources for a new-cheap or good used propellor shaft.
> 
> The one benefit from this whole mess is a stint on the highway (300 km) at
> ~95kmh gave me a fuel consumtion figure of 7.1 litres per 100 km,
> something
> I didn't think was possible in this car. The best I had done previously
> was
> an 8.9, both verified by fuel receipt and kilometre records.
> 
> Suffice it to say the car is my daily driver, feels like a piece of crap
> and
> I need to get it fixed =(.  I'm getting really good at pulling this thing
> in
> and out having done it five times now...
> 
> TIA
> 
> Peter Berrevoets
> 1990 200TQ
> Toronto, Canada
> http://frontpage.home.net/pjberr/
> 
> Javad - what has been the collective experience on the delrin centre
> bearing
> bushing when installed correctly? I'm getting everyone who sees the set-up
> saying that it's too rigid and will never be vibration free. Any other
> installs into a 200Q or other torsen equipped car?
>