[DeTomaso] Clutches- long and short of it

[Göran Malmberg]

What about the bersamel springs or not? This must affect the clearance 
needed.
Goran

----- Original Message ----- 
From: <JDeRyke at aol.com>
To: <chrisvkimball at msn.com>; <detomaso at realbig.com>
Sent: Monday, September 08, 2008 9:14 PM
Subject: Re: [DeTomaso] Clutches- long and short of it


MY standard explanation:
Before replacing any clutch slave, first check the disengagement your
particular car gives. Do this by having someone push the clutch pedal clear 
to the
floor (engine off & cold) while you reach in thru the bellhousing access 
hole
with a flat feeler gauge. Ideally, with a stock system and no wear anywhere 
you
will get 0.040" of clearance. Since a clutch disc has two friction faces,
divide that figure by 2; this means that under ideal conditions (no heat, no 
wear
in the linkage and the pedal completely flat on the floor) you have 0.020" 
of
clearance on each side. This is not quite enough since clutch friction discs
aren't that flat,   most 37-year-old Panteras do not have 0.040" clearance 
and
no one shifts gears with the clutch pedal completely flat on the floor; we
should but it doesn't happen.

All this means that if there's not enough disengagement clearance, the 
clutch
will drag against the flywheel or pressure plate. Drag means that the ZF
synchros are being over-worked. ZF synchros are steel; they not only wear, 
they
equally wear the integral gear-cone they touch when working. ZF gear-cones 
are
not repairable- vendors have tried for years to re-do this part of otherwise
good gears without success. A new gear pair from RBT Transmissions is around
$2000 installed. Conclusion: shifting gears carefully with maximum 
disengagement
pays dividends in longevity.

A typical long-throw slave cylinder will increase the average clutch
disengagement distance to 0.040"-050" on a WORN system. This is still not 
really
enough but helps alleviate clutch drag on the massively expensive trans 
synchros.
The resulting 0.010-0.015"-longer clutch throw will not over-stress 
Centerforce
diaphragm clutch fingers or a stock throwout bearing. The pedal will be
slightly harder to push in.

I personally use a Tilton racing hydraulic throwout conversion that replaces
the slave and its bracket, the bellhousing cross-shaft and its fork &
bellcrank. With a stock clutch master cylinder, I get around 0.060" of 
disengagement.
The system has been in our car for 15 years- I've tried it with both a
Centerforce and a stock Long pressure plate with no problems. It's easier to 
push in
than the stock system due to considerably reduced friction. Dennis sells a
similar system, but hydraulic throwouts are not without problems, 
particularly
during initial set-up. And if something goes wrong, the ZF must come out 
before
you can trouble-shoot. So they're not for everyone.
My 2¢- J DeRyke


**************
Psssst...Have you heard the news? There's a new
fashion blog, plus the latest fall trends and hair styles at StyleList.com.

  (http://www.stylelist.com/trends?ncid=aolsty00050000000014)
_______________________________________________

Detomaso Forum Managed by POCA

Archive Search Engine Now Available at http://www.realbig.com/detomaso/

DeTomaso mailing list
DeTomaso at list.realbig.com
http://list.realbig.com/mailman/listinfo/detomaso