After an August 2003 discussion (below) about "Bad Vibrations" on a
450K mile 350SD the cause of the problem was finally determined to be
a worn driveshaft U-joint, one not easily detected with either
hand-turning or visual inspection.  Howard had it right.  Two
mechanics said they'd never seen a shaft go bad this way - but also
agreed they'd not seen many cars with half-million miles, either.
Could not a find a junk part but did find a (guaranteed) rebuilder out
west.  Months of babying the car and trying to pinpoint the problem
got me around until rebuild - $400/approx. plus frt back/forth.
Wunderbar!

The clearcoat was peeling here and there, the windshield was pitted
and dinged and then cracked last February and, finally, the tranny
gave out.

505,000 miles: new glass, rebuilt tranny, new paint on body and
wheels, repaired driveshaft.  Car looks great - runs like a top.  I am
a happy camper.  All work combined cost 1/4 the price of a new Taurus.
If it just runs another 100K I'm making out OK.  =^)~

Subject: High Mileage Bad Vibration(s)

 
View this article only
Newsgroups: alt.auto.mercedes
Date: 2003-08-01 10:48:03 PST


My '91 350SD (450,000mi) has developed a come-and-go vibration under
acceleration - cruise is smooth, engine runs like a top, no wrecks, no
rear-end problems.  It feels like it's coming from the below the rear
seat
area - the effect is like running over slowdown warning grooves in the
road.
I assume the problem is driveshaft U-joint(s) which, mechanic says,
means
new/used or reman driveshaft.  Anyone with high-mileage driveshaft
advice,
similar experience (or a driveshaft to sell)?  Dankeschoen in advance.

(ps - this is a 350SD that hasn't been a nightmare - gets 25mpg at
75mph
cruise, no leaks, no gasket problems, uses 1 qt every 2500 miles.  I
love
the car in spite of its worrisome reputation and want to keep it.)
Message 2 in thread
From: At work (richard@vrx.news_(Richard_J._Sexton)
Subject: Re: High Mileage Bad Vibration(s)

 
View this article only
Newsgroups: alt.auto.mercedes
Date: 2003-08-01 21:57:12 PST


In article <cGxWa.30214$Mc.2358921@newsread1.prod.itd.earthlink.net>,
Enso <dnathandropthis@hsarmor.com> wrote:

no

seat

the road.

means

advice,

advance.

75mph

love

How are the tires?

Have they been balanced on the car and has it been aligned recetnly?

A good mechanic doesn't suspect bad halfshafts, he tests
for them.

Put two adults in the back anfd load up the truck with heavy
stuff. Go for a drive. Is it WAY worse now? Can you hear
a click click sound?

Take the wheel apart and rotate the halfshalft through 360
degrees. You'll know if you have a bad one by the awful noise it'll
make in one position.

Thanks for repy - tires are good, balanced, rotated, aligned.  The
problem
began with one set of tires and has continued into another set, so I
rule
out tires.  Drove 700 miles north this weekend with one passenger -
returned
700 south with trunk/backseat heavily loaded.  No effect on the
vibration -
it continues to occur only during acceleration and comes with a subtle
"bbzzzzzzzt" sound (or resonance); feels like running over a strip of
closely grooved pavement; there is no "clicking" sound.  Duration of
vibration is about 1 second or less per gear on the upshifts and does
not
happen under very gentle acceleration.

Mechanic checked shaft and supports last Spring and replaced worn or
cracked
bushings in the supports (small improvement for a while); said
flexdisc(s)
had minor age cracks but were not the likely cause; now he says one of
the
U-joints is binding a bit when he twists it and he wants to replace
the
driveshaft - new $900 from MB - no rebuilt to be found, nobody in
Raleigh
who will rebuild one.  I am comfortable with his judgment - any
remanufactured shafts anywhere?  Mechanic says he has used junkyard
replacements in the past and does not recommend them for me (or
anyone).
Message 4 in thread
From: Howard (how82@juno.com)
Subject: Re: High Mileage Bad Vibration(s)

 
View this article only
Newsgroups: alt.auto.mercedes
Date: 2003-08-05 21:51:24 PST

Well, your mechanic seems to have seriously done the leg work to pin
this down to the U-joints, and he has replaced the easier more normal
wear items on the shaft so U joints it is.

Technically, the U joints on my mercedes were not rebuildable either.
As a matter of fact getting the joint itself was seriously difficult,
but there are shops out there to do it. On my car the joint is peaned
in when a piece of metal on the shaft is bent over the U joint and
beaten into place to hold the joint. It's really only meant to happen
once, but on my car we did it twice. I can believe that you can't find
anyone to touch that.

I disagree about not using a junker for this. Alot of these cars died
prematurely and therefore have around 100K miles or a little plus on
them in mileage. The U joints are not serviceable on these vehicles so
there is no maintenance issue. You should be able get the same 400K
miles out of a salvaged part that you got out of yours. The only thing
is that you have to have a driveshaft shop to dynamically rebalance
the shaft with the new piece before you can reinstall the shaft, but
you'll have to do that with a new piece anyway.

Me, I'd get a salvaged part. I think that it pays here as that $900 is
alot of dosh. I also wonder if that's the whole shaft or just the rear
half? I'm betting that it's just the rear half of the shaft that he
wants to buy because that's what has the U joints in it.

Just my thoughts. I am also not besmirching your mechanic. The guy
must be great to have kept this car going so long so well, and the
choice to use a junk salvage part always carries the risk that you
will be back doing this again soon. He's just trying to make sure that
you don't end up unhappy if the part were to fail, so if you wanted a
salvage part it is definitely you accepting the risk. Me . . . I'd do
it. It might not be the right choice for you.

Good luck with that car!!! They're great and congrats on that mileage.

-H
Message 5 in thread
From: Enso (dnathandropthis@hsarmor.com)
Subject: Re: High Mileage Bad Vibration(s)

 
View this article only
Newsgroups: alt.auto.mercedes
Date: 2003-08-06 16:18:37 PST

I think that's about they way he put it - mostly they're fine and
sometimes
they're not...  and he knows I'll bop down another 50K miles this
year.  I'm
thinking about it tho' - it's expensive, that new one.  Mech said he
can get
the 2-part shave redone in town, but the shop won't do mine
(3-piece?).  I
didn't ask why.  Know someone who I can call in your area?  For the
right
price, I'd strip it and ship it.

Thanks for the guidence.
Message 6 in thread
From: Howard (how82@juno.com)
Subject: Re: High Mileage Bad Vibration(s)

 
View this article only
Newsgroups: alt.auto.mercedes
Date: 2003-08-07 15:49:11 PST


"Enso" <dnathandropthis@hsarmor.com> wrote in message news:<b1gYa.528$Ps.43576@newsread2.prod.itd.earthlink.net>...

Mercedes has used three piece drive shafts on their cars off and on
for decades. It was an option on my '72. Some cars had them and some
didn't. They have some advantages in quietness and smoothness, but the
disadvantages in mechanical complexity often off set that. I have no
reason to believe that your mechanic is wrong and you most likely have
a three piece shaft.  I can also believe that noone wants to touch it,
but not particularly because it's a three piece, mercedes shafts are
more difficult to rebuild than most.

I'm afraid that I don't know who would do it for you. Mine was a two
piece shaft, and my mechanic had to lean on his guy to get it done.
It's his realtionship and not mine, and therefore I can't recommend
anybody. I'm really sorry about that.

Balance the cost of labor for installing the shaft against the cost
differential between the new shaft and the salvage part with potential
risk of failure. Seems to me that you shouldn't have too much of a
risk of failure, but it's your analysis not mine. There is always a
risk using salvaged parts.

Best of Luck -

H
Message 7 in thread
From: Howard (how82@juno.com)
Subject: Re: High Mileage Bad Vibration(s)

 
View this article only
Newsgroups: alt.auto.mercedes
Date: 2003-08-04 22:39:11 PST


"Enso" <dnathandropthis@hsarmor.com> wrote in message news:<cGxWa.30214$Mc.2358921@newsread1.prod.itd.earthlink.net>...

Sounds like a bad drive shaft to me too. I have not loked at the drive
shaft of my father's '91 diesel, but my '72 exhibited similar symptoms
before being rebuilt. The tale-tell for me was a lag on acceleration
from a dead stop as all of the sloppy parts loaded up before going.
There was also a whining noise as well as some clunking at high speed
and a general sound of things rattling around down there.

Parts to look out for besides the u-joints on the '72 (and I have no
reason to believe that this is different on a '91 since drive shafts
are fairly universal) are the rubber flex disc, center support
bearing, and possibly a support bushing.

One weird thing on the '72 was the way the U-joints were pressed into
the rear half of the drive shaft. It was not the usual snap rings that
I was expecting and my mechanic was fopced to send it to a driveshaft
specialist who pressed new joints into the old shaft. This was far
cheaper than getting  a factory replacement or even new used. Further,
if your car has this many miles on it, how's the rearend? It could be
some of the rear axle components loosening up as well, and check for
leaking oil back there just to be on the safe side.

As for keeping the car. Good lord, if it hasn't blown up yet, you must
have gotten a good one. I doubt if my father's will be capable of
topping 175Kmiles the way that it's running.

Sorry that I can't give you any specific advice, but a driveshaft is
worth rebuilding, and my '72 feels and handles like a new car with its
repaired.

Have a good one -

H
Message 8 in thread
From: Enso (dnathandropthis@hsarmor.com)
Subject: Re: High Mileage Bad Vibration(s)

 
View this article only
Newsgroups: alt.auto.mercedes
Date: 2003-08-05 08:29:55 PST


<snip>

Thanks for kind reply - mechanic says nobody in town (Raleigh)
will/can
rebuilt the 3-part shaft.  Looking like a new shaft is in my future
unless
someone knows who can rebuilt this one.

Rear end is quiet and very dry on the outside (minor dampness around
the
seal).  An axle boot just tore up and I had it replaced - everything
else
appeared in good order.  Never had a car I liked this much, kept this
long
or drove so far.
Message 9 in thread
From: Enso (dnathandropthis@hsarmor.com)
Subject: Re: High Mileage Bad Vibration(s)

 
View this article only
Newsgroups: alt.auto.mercedes
Date: 2003-08-05 08:13:43 PST


Mechanic says he observes minor age cracks, but nothing to validate
replacement.
 "Wan-ning Tan" <suntan@erols.com> wrote in message
news:3F2CAA7E.8A3E78F3@erols.com...
 Check the flex disc(s).  When were them last replaced?  The front
one
usually bears more torque/damage than the rear one.
 Enso wrote:

   My '91 350SD (450,000mi) has developed a come-and-go vibration
under

   acceleration - cruise is smooth, engine runs like a top, no
wrecks,
no
   rear-end problems.  It feels like it's coming from the below the
rear seat
   area - the effect is like running over slowdown warning grooves in
the road.
   I assume the problem is driveshaft U-joint(s) which, mechanic
says,
means
   new/used or reman driveshaft.  Anyone with high-mileage driveshaft
advice,
   similar experience (or a driveshaft to sell)?  Dankeschoen in
advance.
   (ps - this is a 350SD that hasn't been a nightmare - gets 25mpg at
75mph
   cruise, no leaks, no gasket problems, uses 1 qt every 2500 miles.
I
love
   the car in spite of its worrisome reputation and want to keep it.)