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620crumudgeon

Weird clutch problem

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My son and I have rebuilt the mechanicals on a 1976 620 long bed and installed Beebani’s disk brake conversion. The truck drove great for a couple of hundred miles until the clutch started to drag. When the clutch was depressed a rubbing noise was heard which has diminished but has not disappeared. The throw out bearing lever was loose when the clutch was not depressed. The clutch release point was at the end of the clutch pedal travel then it moved to the start of the pedal travel. The slave cylinder is putting pressure on the throw out bearing lever. When in gear power is applied the clutch slips.

 

The clutch, pressure plate, throw out bearing and clutch master cylinder are new. What could be causing my problem? I’m assuming the transmission will need to be pulled and I am not 

really looking forward to pulling it.

 

 

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hit the bleed screw and see if the clutch fork moves fwd giving you more movement.  Bleed the system.might help

 

I assume you gave a stock clutch made for that vehicle.

 

I assume you put it on the disc on the correct way

Edited by banzai510(hainz)
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The problem is very simple, missing bolts that attach the transmission to the engine. I don't know if replacing the bolts will fix the problem, but that's the obvious place to start. Does anyone know the sizes of the bolts that hold the engine and transmission together?

 

My son was responsible for mating the transmission and engine; this is a great learning opportunity for him. Professionally I've been doing software quality assurance (QA) and test for mission and life critical software and understand consequences of poor QA. This is a great opportunity to demonstrate the consequences of bad QA. I was lucky that the problem occurred at home.

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14 hours ago, 620crumudgeon said:

The problem is very simple, missing bolts that attach the transmission to the engine.  

My son was responsible for mating the transmission and engine; this is a great learning opportunity for him.  

 

He's not alone... this has been reported here a couple of times before.

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M10 x 1.5 not sure on the length. 

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This could be a miss match of the pressure plate and the release collar lengths.  The fingers of the diaphragm on the pressure plate come at different heights above the flywheel. To keep the slave push rod movement in roughly the same place on all clutches, the release bearing collar length is varied. A taller pressure plate uses a shorter collar. A thinner pressure plate uses a taller collar.

 

If your collar is too short the slave will push too far and can fall out. Lengthening the push rod does not help because the clutch arm is limited in it's travel in the opening in the transmission side. The correct collar is the best answer.

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As far as I know the truck is stock, I had never heard of release collar lengths until just now, so thanks for the free education. I also googled 'release collar lengths' and learned about cervical collars. As It turns out you really don't need a longer rod, just a better cervical collar length. 

 

To clarify though, the rod went out and stayed out, kept the fork pushed all the way, and never came back until, the bleeder screw was turned to release  pressure from gas or fluid.

 

Perhaps a little of that is happening here?

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 Clutch arm pressure should push all the fluid back into the master reservoir when pedal is released. Maybe look at why pressure is trapped in the line. Check that there is a slight clutch pedal play or looseness by pushing down on it with your thumb. If no play here the piston in the master can't fully return and let the fluid into the reservoir. Each time you pump the clutch it increases like a hydraulic jack until the slave over extends and jams..

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How loose was the clutch lever when not depressed?

If it had more than just a little play then you should make a longer rod, it should only have a 1/16th inch play after you force the rod into the bottom of the slave with your hand.

 

On 4/2/2019 at 12:15 PM, 620crumudgeon said:

My son and I have rebuilt the mechanicals on a 1976 620 long bed and installed Beebani’s disk brake conversion. The truck drove great for a couple of hundred miles until the clutch started to drag. When the clutch was depressed a rubbing noise was heard which has diminished but has not disappeared. The throw out bearing lever was loose when the clutch was not depressed. The clutch release point was at the end of the clutch pedal travel then it moved to the start of the pedal travel. The slave cylinder is putting pressure on the throw out bearing lever. When in gear power is applied the clutch slips.

 

The clutch, pressure plate, throw out bearing and clutch master cylinder are new. What could be causing my problem? I’m assuming the transmission will need to be pulled and I am not 

really looking forward to pulling it.

 

 

 

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2 hours ago, datzenmike said:

 Clutch arm pressure should push all the fluid back into the master reservoir when pedal is released. Maybe look at why pressure is trapped in the line. Check that there is a slight clutch pedal play or looseness by pushing down on it with your thumb. If no play here the piston in the master can't fully return and let the fluid into the reservoir. Each time you pump the clutch it increases like a hydraulic jack until the slave over extends and jams..

That makes sense, I'll check the pedal Freeplay, thanks alot dude.

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