Re: Overfilling tranny causes damage?

["Scott M." <scottmo@teleport.com>]

Craig,

Back in the good ol days when I rebuilt automatic
transmissions for a living on Detroit iron, i.e. Ford,
Chevy and Chrysler and a few import vehicles, I would run
into a few cars that had a Automatic transmission that had
been overfilled with some rather disastrous results.
Normally the fluid expands a fair amount as it gets hot, so
it is easy to overfill if the tranny is not up to
temperature when checking the fluid level.

If the fluid level gets high enough. the rotating
drums/gear assemblies would contact the fluid and whip it
up and aerate it causing it to foam. This aerated fluid
would be sucked in by the front pump assembly and cause a
dramatic drop in the system line pressure. 

The main forward clutch pack(s)  that allows movement in
1st gear are actuated by applying hydraulic pressure
against a large piston which compresses or sandwiches 
several friction material clutch plates (wet) against some
metal plates to lock the inner hub to the outer driven hub.
This is similar to how a motorcycle wet clutch pack
operates. 

Well, when the line pressure drops, the forward clutch
piston(s) are not getting sufficient hydraulic pressure to
hold the two types of plates together and they will slip
which  will tend to shred the friction material off the
clutch plates in no time flat when you drive the car with
this compromised line pressure.  From the symptoms you
mentioned, "vibration when starting off", it sounds like
you may have a serious problem with one or more of the
clutch packs. 

I don't know how much you need to overfill the Audi
transmissions to have this occur but removing the
transmission pan and inspecting for clutch friction
material and/or metal fragments would be advised. 

HTH
Scott M.
----------
> From: AudiJeep@aol.com
> To: quattro@coimbra.ans.net
> Subject: Overfilling tranny causes damage?
> Date: Friday, November 14, 1997 7:46 PM
> 
> I've had a recurring tranny fluid leak on my '92 100S
autobox. It was coming
> from the seals on the tranny. I had it fixed originally
back in August, and
> it recurred again back in October. I took it back to the
same place, and they
> told me it was leaking out of the breather hole on top of
the tranny. They
> said they used a V8 dipstick intead of the proper V6 one,
and had overfilled
> it. They now have a V6 dipstick, and supposedly now have
the fluid back at
> the correct level. I've had the car back for about a
month now, and the leak
> is back again. The tranny has also been acting up lately
(making vibrating
> noises when accelerating from a stop, shifting weird,
etc). I never had any
> of these other probelms before. When I talked to the
service manager of the
> garage today, he said the only damage overfilling the
tranny will cause is
> from the fire that will occur if the excess fluid gets on
the manifold and
> catches fire. I think this is bull#$%&, of course. So
what damage can
> overfilling the tranny cause? TIA.
> 
> Craig
> '92 100S (67k)