[DeTomaso] Shifting

[Himes, Terry (397C)]

I do that was well.  Also, I have to shift into 2nd before shifting to 1st if I sit at a traffic light too long in neutral.
The weirdest thing that 1st gear would run up.  But I have accepted as part of driving my P.
And I have a new master, a new clutch and my ZF was rebuilt and safety wired.  Go figure.



Terry W. Himes
JPL Jet Propulsion Laboratory
Deep Impact Sequence Team Lead
Deep Impact Spacecraft Engineer & Activity Lead
Phone: (818) 393-6261
Cell:     (818) 653-8213
Fax:     (818) 393-3147
thimes at jpl.nasa.gov<mailto:thimes at jpl.nasa.gov>


From: Charles McCall <charlesmccall at gmail.com<mailto:charlesmccall at gmail.com>>
Date: Friday, February 7, 2014 11:42 AM
To: 'Peter Cajthaml' <pcajthaml at gmail.com<mailto:pcajthaml at gmail.com>>, "detomaso at poca.com<mailto:detomaso at poca.com>" <detomaso at poca.com<mailto:detomaso at poca.com>>
Subject: Re: [DeTomaso] Shifting

I ALWAYS shift into first before shifting into reverse, as it helps a ton, and may even solve your problem

From: DeTomaso [mailto:detomaso-bounces at poca.com] On Behalf Of Peter Cajthaml
Sent: viernes, 7 de febrero de 2014 20:17
To: detomaso at poca.com<mailto:detomaso at poca.com>
Subject: Re: [DeTomaso] Shifting


All: thanks for the great advice, and the lively discussion; I will start by bleeding the system and looking at the master cylinder.

Also, off-the board I received advice to try the 2nd-1st-reverse shifting sequence when the problem occurs.  Seems easier than turning off the engine!




Peter
#2761

>>>The fact that it goes into reverse with the engine off leads me to

believe that the issue isn't a linkage problem, but rather, a problem with

insufficient clutch disengagement.   An easy way to tell, though, is to simply

remove the shift gate, and see if that makes any difference.



Pantera vendors sell an aftermarket shift gate which has the same lateral

dimensions as the stock one, but is considerably thicker.   This illustrates

a fundamental lack of understanding of basic geometry.   The thicker

(taller) the shift gate is, the less lateral movement will be allowed before the

shift lever hits the edge of the gate.   In order to allow equal side-to-side

movement as a stock gate, the opening has to either be wider, or beveled to

match the angle of the shift lever--neither of which they do.



So, if you can pull your shift gate off, then cheerfully snick into all the

gears including reverse, the problem is either your shift gate (if it's

aftermarket), or simple (but maddening) adjustment of the linkage.   If you

have a stock shift gate, it may well be that your shift lever isn't perfectly

centered, and needs to be adjusted ever so slightly to the right.   You want

to have enough throw to the left to get it into reverse, but you don't want

it adjusted so far that 4th and 5th become problematic.



Since removing the gate is an easy test, do that first.   If that fails to

fix things, then the problem is almost assuredly insufficient clutch throw

(disengagement).   The synchros will take a bit of a beating and will allow

shifting up and down the forward gears without 100% disengagement (although

that creates wear, not a good thing) but reverse is normally recalcitrant

unless the clutch releases completely.



A PCNC member was recently struggling with this issue, and like you, he had

replaced his slave cylinder as well as his master cylinder.   In the past,

I've said that the function of the clutch is adjusted exclusively at the

slave cylinder, and the master cylinder pushrod adjustment is only used to

adjust the resting location of the pedal.



While this is true of the early cars, I failed to take into account the

monkey-motion clutch effort reduction linkage which was introduced with the

Pantera L.   While your car is early enough that it wouldn't have had it from

the factory, mine is too, and yet mine had it, apparently retrofitted at some

point.



There is a "T"-shaped hoozit that acts as an intermediary between the

clutch pedal shaft, and the pushrod on the master cylinder.   Once you think

about it, it's easy to see that this hoozit needs to be oriented at about a

45-degree angle (towards the rear) at rest; depressing the pedal moves it

through an arc, and it winds up at about a 45-degree angle towards the front.

This provides maximum stroke of the piston.   (The actual value may be

something other than 45 degrees, but even if it's 30 to the rear, then 30 to the

front, the point is simply that it needs to be more or less the same).



If the clutch master cylinder pushrod is too short, the arc then causes

movement in the wrong direction.   As the pedal shaft acts on the back of the

piece, the front of it, rather than (mostly) going forward, instead will

(mostly) go down towards the ground, resulting in measurably less master

cylinder piston movement, with a commensurate lack of movement at the slave

cylinder.



So, first check to see if you have this piece in your system.   A photo of

the system at rest is attached, taken from the perspective of the center of

the car, looking directly outboard.



The gold-colored piece at the bottom is the support for the T-shaped piece,

whose long leg attaches to it.   The two short legs of the T-shaped piece

are attached to the clutch master pushrod, and to a pair of links which are

attached to the shaft which is rotated by movement of the clutch pedal.



(Chuck Melton has a terrific video of this beastie in action, on the

Provamo website.   Perhaps Chuck can post a link?)



The Ford TSB #10, article 89 (page 9) gives the optimum length of the

pushrod going into the master, of 2.91-2.95 inches, from the center of the eyelet

on the pushrod clevis, to the mounting surface where the master bolts to

the aluminum pedal bracket.



(Article 88 prescribes a length for the slave pushrod of 3.07-3.09 inches,

from the center of the eyelet to the bullet nose of the pushrod, but this is

something that would be adjusted to compensate for clutch wear, different

installed finger heights for different brand clutches, etc.)



If you don't have the effort reduction kit, you can still see how proper

pushrod length is important.   You want as much of the rotational motion of

the clutch shaft as possible to be translated into horizontal motion, which

compresses the master cylinder.



Assuming there is no overt mechanical/adjustment issue, and the seals are

still holding up, then the likely culprit is air in the system.



> <I replaced a bad clutch slave cylinder about 5 years ago with the stock

> OEM unit.  I recently saw that an upgraded stainless steel slave is

> available - would that improve the situation?

>

>>>The material isn't important.   Some aftermarket slave cylinders boast

'long throw' which they achieve by using a smaller-than-stock piston.   This

results in greater extension for a given amount of master cylinder (and

clutch pedal) movement, with the tradeoff being slightly higher effort required

due to the reduced mechanical advantage.





> > If not, how do I adjust the clutch so it disengages completely when

> hot?  I plan to change the fluid and bleed the system again, but have done so

> many times before without an improvement.

>

> >>>An important consideration is clutch slave pushrod adjustment.   When

you depress the pedal, does it descend a notable distance with relatively

light pedal effort, before actual clutch action starts to happen?   If so, then

a percentage of your clutch hydraulic action is being wasted, by moving the

'fingers' of the clutch fork through free space.



Have you ever had your gearbox off to see what it looks like in there?

Here is a drawing from the factory parts book, showing the lever that attaches

to the slave cylinder, and the shaft that it is attached to; inside the

bellhousing this shaft is pinned to the clutch fork:



http://www.panterasbywilkinson.com/images/final_catalog/gif/ill13a.gif



You want the fingers of this clutch fork to be very close to, but not

touching, the throwout bearing when the clutch is engaged (foot off the pedal).

When you step on the pedal, you want the fingers to initially pass through

free space, a very short distance (perhaps 1/8 inch or so), and then touch

the throwout bearing; further pedal movement results in the fingers

depressing the bearing which in turn releases the clutch.



If you have too much free travel here, when the clutch master bottoms out

(pedal almost against the carpet) the clutch won't be fully released.   This

can be felt easily enough from behind the wheel, if the clutch engages with

the pedal very close to the carpet.   This also can be felt at the start of

pedal movement, as very gentle initial movement with not much really

happening, followed by greater resistance.   Ideally, you want something like 1/2

or 3/4 of an inch of clutch pedal movement before clutch things start

happening.



The aforementioned TSB has very poor guidance on establishing the amount of

free play.   It prescribes various amounts of clearance and lengths of this

and that, without really describing what you're trying to achieve, and how

to adjust things in order to get what you want.



Hopefully you can get some relief from this problem.   There is no good

reason for a car to grind going into reverse, much less be impossible to shift.

  It's just a matter of finding the cause and eliminating it.



Good luck!



Mike

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