[DeTomaso] Shifting

Fri Feb 7 14:53:54 EST 2014

Until they make a synchro reverse, you best not go directly from neutra into reverse. Basic Driving Course 101.
On Feb 7, 2014, at 11:49 AM, Himes, Terry (397C) wrote:

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