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Clutch fork clicking

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Hi All,


Noob here with a few questions. I've got a '73 620 with a L20b from a 77KC, a 5 speed that originally mated to a KA24 (not sure if e or de). Clutch and flywheel came with the L20b, so I assume I have a 225mm flywheel/clutch. The bell housing and clutch fork I'm not sure where they came from.


Let's go back to Friday. Driving home from work, my slave cylinder craps all of the fluid out the rubber boot. When under the truck I noticed that the push rod is a threaded one with the rounded nut on the end. The clutch fork does not have a hole (is this a "B" type?). Anyway, installed the new slave cylinder and I had to use the threaded rod from the old slave cylinder because the new one was about 3/8" too short to disengage the clutch.


Based on what I've read while searching, I should have a few tenths of play in the clutch fork when the clutch is engaged (slave cylinder rod fully retracted). The problem I have is I have to thread the nut on the push rod out about 1/4" past the end of the rod to the point where it's putting pressure on the fork. When test driving it, I get a loud clicking sound from the fork while the clutch is engaged. If I push the pedal in, the sound goes away.


I've tried adjusting the nut back but then I lose the ability to shift. If I adjust forward the click gets louder and I'm wary of preloading the clutch too much. The pic is a link to a video I shot yesterday of the fork/slave cylinder. You can't tell by the poor iPhone video quality, but the fork/pushord are shaking around like a crazy son of a bitch. One thing to note: there was no clicking before the old slave cylinder went bad - only after I installed the new one with the old threaded pushrod. Old and new slave cylinder are the same length and dimensions of course. What the hell can this clicking be? Does it sound like I have the wrong sized release collar maybe? Thanks in advance guys. -Rob



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No 71-B or 71-C tranny had a hole in the clutch arm with an adjustable push rod and spring.


Seems that when you changed the slave the problems began. I would guess that you don't have the correct slave for iot.


Does your old or new slave have a spring on it that also goes to the clutch arm?




This is important... does the hydraulic flex line come into the end or into the side of the slave????

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Neither the old or new slave have a spring, and both had the flex line attach to the end of the slave next to the bleed screw (facing toward the front end), like your pic. The body of the new slave is the same length and dimensions of the old one. The only difference was that the push rod on the new one was not threaded and shorter than the threaded rod on the old one, which was the reason I swapped in the the threaded on after I installed the new slave. The non-threaded rod was too short. The threaded one is too short unless I turn the nut out that 1/4" past the end of the rod which in turn puts slight pressure on the fork.

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Other possible issues than just the slave????....

The clutch fork shouldn't be "shaking around like a crazy son of a bitch"???????

Almost like the throw out bearing/pilot bushing is compromised ???....clicking could also be a bent finger on the clutch?........etc....etc

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Im thinking the collar size was different. thus making the rod not fit right.


I assume the threaded rods are only on the early 510/521 and maybe early 620s with l16s or so. But Im not a 620 expert.


to me the slave cyl are pretty much the same. trucks have the hose from front and cars come from the side. Thats about it. I assume the rod come with the spec type of vehicle you orddered it for so I assume a 620.


key is to find the stock diapram height.


a early 620 T/O Collor and layter L20b T/O colloar are different heights plus the T/O bearing its self is different as the ealy 620 used a 200mm set up


I persoanlly like the threaded rod ealry 510 clutch fork. Just in case of such a thing.

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The prolem is that everything worked before last Fiday when the slave craped. Only thing changed was the slave.


I guess it is possible this was jury rigged to begin with because the release collar was wrong to begin with.

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I guess I find out this weekend. I have no idea what the bell housing came from, other than it came off of a 5 speed tranny to fit the KA24 gearbox in there. Not sure if the release collar and fork came from the old tranny attached to the L20B, KA24 bell housing, or from the 5 speed. Thanks for the help guys.

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I search and search and always end up with the same results. One more question for you guys (I really appreciate the input so far). Assuming that I have a 225mm clutch and flywheel, what should the measurements (length?) of the release collar be? I've been perusing the interwebs and I cannot find anybody that sells the collar, only the bearing. Is there a Nissan part number for the release collar for a 77 620 L20B? Or am I going to need to pillage this from the junk yard?

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^^Yup, going to do that before I purchase anything else. Thank you sir.


Edit: actually, what Mike said. You got in before me, Hainz. Good idea though. I'm going to mess around with it to see what I can do. I'm really interested though in what it looks like inside the bell housing. That fork is shaking pretty damn hard, so I have a feeling that something went sideways in there first that I wasn't aware of and eventually killed the slave.


I wish I could isolate the clicking sound. I can't tell if it's coming from inside the housing and being transmitted through the fork, or if it's the threaded nut on the end of the pushrod clacking against the fork itself.

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Well, I dicked around with it some more after work today. I gave the niue on the slave pushrod another full turn, started it up and the clicking was definitely quieter. Drove it around the block a few times to run it through gears and the shifting still felt notchy, so I put the truck back the jackstand and gave the nut another full rotation out plus a half turn. Buttoned it all up and went for a drive. No clicking, and smooth shifting. Problem solved.


I'm still going to drop the tranny this weekend to check things out in there only because I had to adjust the nut out so far. It doesn't seem right to me. Maybe the collar is the wrong size or the fork is bent. What ever it is, I just want to know that everything is in tiptop shape.


Thanks again guys for your help. -Rob

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