i have had inexperience drivers that either have forgotten to push the clutch to stop or have started out in too high of a gear which has resulted in the anti-stall clutch to either build up pressure or cause it not to engage the pressure plate so not allowing me to get the truck into or out of a gear.

 

Welcome to the forum. Fill in your signature so we know what kind of truck you have.

Anyway, the clutch has a hydraulic linkage. You might check fluid level and look for leaks, but I'd guess you may end up replacing the linkage.

 

the truck in question is a 2006 3500 ram with a 6 speed manual

 

May have a slave issue, or pilot bearing (though you will hear the pilot bearing flying around most of the time.)

 

Master cylinder has a check valve below it and locks up. Replace hydraulics with Southbend set. Approx. $350. Common problem. I 100% guarantee that is the problem. Search my numerous posts on the problem.

https://www.dieseltruckresource.com/...o-t239668.html

 

There is no check valve in the system. There is a compensation valve internal to the M/C which, in the first 2mm of pedal stroke, seals off the M/C reservior from the rest of the line running to the S/C.

I suspect the supposed "check valve" you think is on there, is the valve "looking" piece that is located outside the M/C is attached immediately to the M/C inline to the clutch line. It's a DAMPER, not a check valve. It's there to merely fight pedal vibration.

 

"A pressure compensation valve is capable of distributing of an output pressurized fluid of single pressurized fluid supply source to a plurality of hydraulic loads. The pressure compensation valve is constructed with a check valve portion formed by providing, in a valve body, a valve for establishing and blocking communication between an inlet port and an outlet port."

Couldn't that be considered a check valve since it prevents the flow of fluid?

Also there is only one load, the slave cylinder. So multiple outlets aren't necessary.

If replacement of the hydraulics solves the hard pedal problem, one would believe that the cause lies within.

Give Larry at Southbend a call. He is very familiar with the problem and can repeat the explanation I gave above.

 

Which part?

 

Your compensator valve.

 

Section 6-5 of the Doge Service manual:
Clutch will not disengage properly.
Number 7: clutch master or slave cylinder failure.
Replace hydraulic linkage assembly.

 

No, because as soon as you release the pedal, the fluid in the line is open to the reservior.


I'd venture to say it's a failure of a different internal component.



Won't be necessary because I know more about the system than he does. I designed and released the system for the G56 back in the day.

 

I see. So you would be in a position to explain how the pedal can become rock hard after a rough engagement such as releasing the clutch too fast from a stop. Or after power has been increased, and the clutch slips, the pedal becomes rock hard and unable to push it in to release the clutch.

I really look forward to seeing the explanation because I looked hard for two weeks and tons of phone calls.

 

For one, the SAC, always seemed to have odd behaviors that were hard to replicate. At least in early development. If you increased the power, it slipped, wore the clutch face enough it pressure plate reset again or at the change point, it's possible it needed to flex or be bumped, moved, etc to "slip" into the next set position. Until it set up again, actuation could be limited. (ie it's bound up) It's hard to explain without pics and such, which I can't provide. I've seen this happen on a couple occasions back in early 02 in the development stage. However, needless to say, there was a number of refinements done since to the PP.

Interesting tidbit, is that, for the first time in the history of the company, they didn't wear out a clutch over the life of any testing. The SAC is a good unit for a stock truck. The clutch wear is kept minimal because the pedal load/throw is consitent throughout the life of the clutch.

Like every part, on occasion a quality spill happens. Possible such a issue arose and you have a part that is bad. or occassionaly bad. You mention quick actuation causing problems. Depending on conditions at the point of actuation, like side stepping the pedal, it may have drew in a extra fluid into the line before the comp valve opened. Then if you stepped on the pedal and actuated the clutch, it's possible you over stroked the clutch, binding the self adjustment feature. Or maybe when the clutch was actuated the first time on installation at the plant, the retainer on the slave rod didn't break adequately and the rod was misaligned with the release lever. And it's stuck in that particular position, close to the intended pocket, but just off. Hard to say what exactly would happen, but it could range from failure right away by blowing the slave rod out, to occasional difficult operation.

It's also possible the piston bound up, broke or the comp valve retainer broke and bound up with the piston. (ie floating piece of plastic in the MC) The "check valve" as you so refer to is the comp valve. It resembles a match stick in size. Has a rubber stopper on the end of it which is the sealing surface to cut fluid flow off to the reservior. Load applied to it... again it's the size of a match stick and can't stop the pedal. The resistive load stopping the pedal can only come from three locations. The M/C, S/C or the clutch itself. The M/C would be a failure of the piston. The S/C could be the same, the piston, or the release lever/SAC binding.

Also note, if you are the type of person that rides with your foot on the clutch pedal all the time, this is bad and can lead to overstroke of the clutch depending on different conditions like low temps.

 

I'm with ya so far. Let's try to narrow down the conditions. I wasn't abusive or destructive in operation, sidestepping. I have lots of hours in dump trucks, lots of hours with heavy loads in punishing environments. So operation is not an issue. "Clutch is either in or out, and **** sure not a foot rest!" I remember that from the guy who taught me how to drive. So, low RPM engagement, idle or just above, while letting the momentum of the engine start the truck into motion. Once in a while the engagement is too abrupt, not killing the engine but nearly. Definite vibrations and added power through stock fuel management. This is one situation that caused the stiff pedal. Possibly an added power / torque situation causing slippage? Since you were in on the design, I'm sure you're familiar with the no throttle input starts where the ECM increases fuel delivery thereby automatically adjusting power levels to get the truck rolling. Kind of rolling into the throttle as you engage the clutch, but with more accuracy and consistency than a human. If that peak in fueling could reach a level that would cause flex or deformation in the clutch face, would the self adjusting feature cause pressure to be exerted in such a way as to prevent the hydraulics from moving? The stiff pedal is really that stiff. Like no movement in the slave cylinder. You can feel pressure and slight pedal movement, 1 mm in travel, like the line is taking fluid and expanding. If there was no movement, I would guess master cylinder blockage. But another point may be a valve that might allow a slight amount of fluid to pass creating the same feeling. Now after the truck sets turned off, the pedal is rock hard, 10 minutes later, normal operation. Two possible causes; thermal variation, doubtful over 10 minutes, or hydraulic bleed off. So that's how I arrived at the hydraulic cause. The leak, bleed off, is internal. It has to be. Over several instances, 5 times, no loss of fluid was observed.

Ok, long but hopefully narrows the picture.
Awaiting reply.

 

Regardless of the cause, an occurence of this stiff-pedal syndrome while in traffic could be cause for a safety recall, or, in the case of property damage, injury, or loss of life, a lawsuit. This is an issue that should be properly addressed by Chrysler corp. I found the stiff-pedal syndrome unnerving the first few times it occurred.