Re: Rev matching

["Bernard Littau" <bernardl@acumenassociates.com>]

Hi Russ,

It would be a good idea to practice rev matching shifting before your clutch
goes.  It saved me a month ago when the clutch failed on my '71 Ford
three-on-the-tree pickup.  Had to drive it home with a combination of crank
the starter in first and start the engine while getting the truck moving,
and rev matching shifting.

BTW I haven't had the heart to try starting my Audi while in first -- the
5k's have _tiny_ starter motors.  I'll do it if I have to.

On to rev matching shifting.  I suggest you go down a long, level, uncrowded
stretch of road and do the following.  In 3rd gear at about 3000 rpm, hold
the car at a constant speed and gently try to push the gearshift out of 3rd
to neutral.  You should feel some resistance, as the transmission is
slightly loaded by keeping the car at a constant speed.  Don't force it.

Now, while holding a constant speed down the road, put some pressure on the
gearshift to push it from 3rd to neutral, but not enough to actually move
it.  Gently ease off the throttle, keeping the pressure on the gearshift.
As you transition from engine powering to engine braking, you go through a
no pressure on the transmission point, and the gearshift should pop out with
the slight pressure you are putting on it.

You might try this a few times.  You are getting a feel for the pressure it
takes to shift out, and some feel for throttle control around the no load on
the transmission point.  To unshift, you don't worry about rev matching
since the engine and transmission are locked at the correct rev match, but
the load on the transmission is what is important.

To shift back into 3rd from neutral, you need to match the engine rpms to
the speed expected by the transmission when they are engaged together.  Get
moving at the 3000 rpm in 3rd rate, and pop the transmission into neutral
and let the engine go to idle.  Gently, using the same amount of pressure
you used to unshift, try and push the gearshift into 3rd.  Of course it
won't go.  Keep the gentle pressure on the gearshift towards 3rd, and slowly
raise the engine rpm.  When you get to the correct rpm, the gearshift should
just pop into 3rd.  You have to move the rpms up at a slow enough rate that
the system has time to react.  If you gun the throttle, it won't engage even
though you go past the rev matched point.  Be aware the car is slowing down,
so it may pop in at 2500 rpm.  Slowly move the rpms, Gently push the
gearshift.

That is the brut force lesson.  Note that disengaging is as important as
engaging.  In fact, you are more likely to damage the teeth on the
transmission's gears by a bad disengage than by trying to engage.  That's
why we did the gentle disengage first.  Gentle is the key to avoiding
damage.

You are not doing your transmission a favor by trying to engage at an
incorrect speed, so you want to be as close as possible to the "correct" rpm
before you do your gentle pushing and throttle control.  Modern
transmissions have synchro-mesh -- think of it as a little clutch that
engages as you try to go into gear.  The little clutch tries to force the
transmission's internal gears to spin at the correct rate to match the
driveshaft.  Synchro-mesh does rev matching for the internal parts of a
transmission.  The synchro-mesh working is the whine you hear from your
transmission when you attempt to shift into first at 20mph with the clutch
in.

On a level surface with the engine idling, if you gently try and engage
first without the use of the clutch, you can make the car move forward by
using the synchro-mesh.  Go ahead and try it once.  You can actually push
pretty hard on the gearshift and abuse the synchromesh.

Pay attention to the rpms you are running at in various gears for a while,
especially when you start from a stop.  I often find myself shifting a 3000
rpm, and then the next lower gear engages around 2000 rpm.  For a final
exam, you should be able to take off from a stop in first using the clutch,
go up to 3000 rpm and shift without clutch from first to second, go up to
3000 rpm and shift from second to third, and your passenger should not
notice if you used the clutch or not.

Best,

Bernard Littau
Woodinville, WA
'88 5kcstq

-----Original Message-----
From: Jeff Mruss <rmruss@pangea.ca>
To: 'Quattro List' <quattro@audifans.com>
Date: Wednesday, August 11, 1999 9:00 PM
Subject: Rev matching


>I've seen lots of posts referring to rev matching (usually when talking
about a clutch that died), and I understand the basic concept of matching
the engine speed to the gear you want to shift into, but what I want to know
is - how do you do it?  I don't plan on making a habit of it, but it would
be a pretty useful thing to know if my clutch ever failed.
>
>TIA,
>
>
>Jeff Mruss