[A4] A4 clutchless shifting
tyson at up-times.com
Fri Apr 20 14:03:46 EDT 2007
Robert, I have to politely disagree. I have seen both failures happen many
times from people with bad shifting habits. The only Audi that suffered this
fate under my whiteness was a 4000CSQ, but I have seen it plenty of times on
other cars. An ex coworker of mine after sitting at a light for quite a
while went to go into gear and the car would not move at all and smoke came
from under the hood. She was sitting for about 8 minutes with the clutch
down. The car drove fine before and after the clutch cooled down, I know
that car drove for at least 10,000 miles. I also have a fried that buys
"mechanic special" cars that need simple labor-intensive things done. I help
him sometimes and I have seen at least a dozen cars with busted throughout
bearings and very low miles. He buys mostly from private owners and they
tell him that they sit with their foot down.
Although you are right - in a well designed and properly adjusted system, it
is not that huge of a deal - but that is rarely the case. Wear contributes
to minor changes, which even an experienced mechanic may not find because it
is difficult to tell exactly what is going on under the bell housing.
Furthermore, although the CV joints are not actively lubricated, they are
also sealed and enclosed - unlike any throwout bearing that I have ever
seen. Ever have the rubber boot break on a CV joint? It loses lubrication
and fails shortly after. Thowout bearings are not designed to spin all the
time and their lubrication is not very well enclosed.
Technical Manager, Uptime Technical Solutions LLC.
tyson at up-times.com
From: Robert King [mailto:gt40mkii at gmail.com]
Sent: Friday, April 20, 2007 8:01 AM
To: Tyson Varosyan
Subject: Re: [A4] A4 clutchless shifting
On 4/20/07, Tyson Varosyan <tyson at up-times.com> wrote:
By sitting at a light with your foot holding the clutch pedal you are doing
serious damage to the clutch system.
Sorry, but I've GOT to disagree with pretty much everything you posted. If
you like, I can get an authoritative quote from a good friend of mine who
designed drivetrains for Ford, but for now I'll just say:
1. The throwout bearing, while being permanently lubricated, is more than up
to the task of being engaged for extended periods. Because it doesn't have
a pressurized oil system does NOT imply that it isn't intended for extended
operation. You do realise that CV joints and wheel bearings are permanently
lubricated, right? I guess we shouldn't drive our cars for extended periods
for fear of wearing out the wheel bearings, either.
2. Unless its malfunctioning, there is almost ZERO friction between the
pressure plate and the clutch disk. While its true that the pressure plate
doesn't move much (about 0.125" to 0.25" for a diaphragm clutch -- a little
more for a Borg & Beck-style clutched used in older cars,) there doesn't
need to be much to fully disengage the clutch. If there were significant
friction between the clutch plate and the pressure plate and/or the
flywheel, you'd experience creep as you sat with the clutch in in 1st gear
on a flat, smooth surface. This simply does not happen.
While in THEORY, the drivetrain is under less wear when idling in neutral
with the clutch engaged (the clutch assembly is locked up and the throwout
bearing is not spinning, but the internals in the transmission are.)
Practically speaking, however, it's a non-issue.
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