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11 replies

Grinding noise when shifting : syncs or clutch ?

M matt78Member
Hello.

Here is my concern : I experienced some grinding noise on 1st (not to speak about reverse, but I know there's no sync on it), 2nd and 3rd gears (4th and 5th seem to be ok).

In order to avoid going into big expenses right from the start, I began by checking the clutch command : I replaced the master and slave cylinders, and changed the red plastic tube for a braided hose - all sourced from PIM.
Everything is ok when cold, but when the temperature rises (after approx. 15 or 20 miles riding), the grinding noise comes back.
The clutch seems to disengage correctly - no creeping when in gear, for example.

Having decided to get the transmission inspected, I rode the car yesterday to thoroughly identify all the issues, as I don't want to discover a new one after a partial gearbox rebuild...

Doing so, I discovered that the grinding noise (in 2nd and 3rd gear, at least) seems to depend on the de-clutching speed, i.e. if I depress slowly / calmly the clutch pedal, grinding noise occurs maybe 8 times out of 10. On the contrary, should I depress very quickly the pedal and shift (quickly, too), there is no problem...

I'm therefore no more certain that it is strictly sync-related : could it be that the new clutch command is still faulty - or out of adjustment ?
I'm aware that the first syncs to be at stake would be the 2nd and 3rd as they are the more loaded, thus likely to be worn and in need of an overhaul, but the cost isn't the same Frowner

Did you encounter this kind of problem ? What's your opinion about this ?
Thank you in advance for your replies.

Regards,

Matt
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joulesjoules"Racing is Life, anything before or after is just waiting" - Steve McQueen
Fortunately what you describe does not sound like a transaxle issue, assuming you have verified and changed the gearbox oil!

Sounds to be clutch system, perhaps a small amount of residual air in the hydraulics? Can you check the clearance of the pressure and friction disc while someone presses the clutch, do it both hot and cold and see if it changes, ideally you want about 0.040".

When static how easily does the shifter move through the gate? Have you checked all the shift rod linkages, u-joints and trunnion bearing?

Julian
forestgforestgMember
I believe you have a clutch disc that is slightly dragging. This could be due to an improper clutch assembly being installed or a problem with the hydraulic clutch system. Your description of a rapid depression of the pedal being better than a gradual one is symptomatic of a failing clutch master cylinder.

I believe that the reason it works better when cold is that the trans-axle grease is stiffer and creates some drag on the gears that lessens as the oil warms. One other possibility is the clutch friction disc binding on the trans input shaft splines. A long throw slave cylinder may help but will have an increae in clutch pedal effort.
matgmatgMember
Matt78

Def you want to measure the gap a mentioned by the team notes, that is less expensive to fix

However, just a thought for further investigation..as I went through a gearbox situation..

quote:
Everything is ok when cold, but when the temperature rises (after approx. 15 or 20 miles riding), the grinding noise comes back.


The thing with the synchros is that the inside when new has a special surface which has some roughness, so when sliding during gear shifting oil is kept to speed up the destination gear to avoild grinding. If the synch is rottet like mine where there is not enough "oil hold" to provide this service. When oil is cold it appears stiffer hence it provides the service but when hot it slips to much..I replaced all 5!


Matthias
M matt78Member
Thank you all for your information.

Following your advices, I measured :
- the gap : 0.040" gauge slides between the disc and the flywheel
- the slave cylinder stroke : 16.5 mm.
At first sight, nothing especially out of adjustment...
Nonetheless, I noticed that the angle value between the clutch axle arm and the slave cylinder axis was greater than 90°, even at full stroke : so, I rotated the arm by one notch.

I'll check the new gap tomorrow - maybe I'll need to lenghten the rod - but I'm not sure that it would significantly improve Roll Eyes

I'll keep you posted.

Matt
bosswrenchbosswrenchMember
What ZF lube are you using? The Factory Manual says 75-wt regular, and the ZF was built well before synthetic lubes were invented. I have heard that super-slick trans lubes or very thin 'racing' lubes such as Redline causes shifting difficulty in some ZFs. The same lubes can FIX shifting problems in other ZFs, so this is a confusing problem to solve via long distance. My '72 ZF shifts fine using Castrol 70-wt with a small amount of LSD slip-agent in it.

Another suggestion: early Panteras and Mangustas with the transition dash-1.5 ZF used a 1-1/16" 10-spline disc (GM) while production Panteras and their ZF dash-2 use a 1-1/8" 10-spline Ford disc. The spline sizes are only nearly impossible to sort by eye. So some "equivalent" clutch discs fit sloppy and wobble on a later ZF input shaft while others are a rather tight fit. This can make disc wobble and synchro drag worse.

And in fact, synchro wear can make ANY clutch drag if it gets too bad. We're dealing with a 45-year-old mechanism bolted to a high-torque, high powered engine here. I hesitate to point out that most such troubles like this can be avoided by using parts from recognized Pantera vendors, who can also inspect the all-steel synchros for unacceptible action. There are a very few known European Pantera specialists. Good luck-
M matt78Member
I must admit that I don't know the lube which is currently in my 'box... So, I'm sure that everybody will advise to replace it first. I'll do it (according to your remark, it's not easy to know which one to use !), but don't believe in miracles, esp. in the mechanics field Wink

Regarding the clutch disk, I don't know its make/model. I only can see that :
https://drive.google.com/open?...31yOAmXxPVGzM-bRA8A2
Of course, unable to say if it's fitted tight or loose.

Since I bought the car, I always sourced the parts from vendors mentionned on this forum. And, yes, it's VERY difficult to find specialists here...

Matt
M matt78Member
Hello.

Here's the updated status : I replaced the leaking Master Cylinder (bought from PIM : new but already leaking Mad ) by a new one (Ferodo Europe).

No more leak, but what a hell of a bleeding session ! I finally got it by putting 0.5 bar pressure on the MC, lifting the rear of the car and continuously taping on the circuit in order to help moving air bubbles.

At first start, it didn't seem to be enough, because the pedal was too soft on the first half of its stroke : I couldn't manage to shift in reverse nor 1st gear... After many attempts and maybe 5-10 minutes idling, the pedal got more and more firm. I guess that engine vibrations helped to free the lines and circuit components from remaining bubbles...
The following 45 miles road test confirmed that all is ok now.

Many thanks to all of you for your support !

Matt

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