anthony_c

clutch fork swap?

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    • recently installed a new clutch and slave cylinder into a 5 speed and i'm having trouble getting the clutch to fully disengage.
    • the problem visibly manifests itself at the slave cylinder. when the pedal is fully depressed i'm only getting 1/2"+ of travel at the fork.
    • pushrod at the master cylinder is fully extended.
    • the transmission has been pulled again and we've verified that all of the parts are for a 5 speed coupe. collar and pressure plate match.

    current theory is that the pushrod on the new slave cylinder is just too short.

    the mechanic has suggested using an adjustable slave and fork from a 240. has anyone tried mating a 240 fork to a 280 collar, bearing, and clutch?

    Edited by awconroy

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    I have seen this with other aftermarket slaves. You are correct. Typical mainland china quality.... looks like a master, feels like a master but it isn't a master.

    This happened to me on my RAV4. I just took a longer rod from a spare Z master and swapped. A lot of these parts are interchangeable on Toyota's, Nissan's, Mazdas and Hondas.

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    You should send that bill for pulling the transmission and all your time troubleshooting to China.

    Seems like our suppliers are content to pass that crap onto us.

    Can you imagine if it was the brake master and it was too short.... sadly I bet it has or will happen.

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    well, before we all start blaming a nation of several billion people for my clutch problems...this slave cylinder was purchased from Courtesy Nissan.

    I also bought one from Arizona Z and it was identical.

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    I've got the opposite challenge! 1972 240z with a 1977 280z 5speed. I'm using the 280z clutch, pressure plate, collar, and non-adjustable slave. The clutch seems to disengage very quickly (within the first third of pedal travel). Basically I only have to push the clutch pedal down 2 inches and I fully disengage. The clutch doesn't seem like its slipping at all (4th at low speed, throttle floored and now slipping). Any thoughts on this one?

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    You wont need a fork from a240Z. The 240 and 280Z clutch forks are the same dimensionally except the early 240Z has an extra eye on the outer end for the return spring and the 280Z doesn't have a hole for the pushrod to go through. That version also has the adjustable push rod.

    I had a similar problem with the slave cylinder I replaced a year ago. The push rod was too short.

    I removed the two bolts holding the slave cylinder and pushed it towards the clutch until it bottomed out. I measured the distance between the holes in the slave cylinder and the threads in the bell housing. Then it was simply a case of measuring the rod and adding the difference. I made it 10mm shorter to allow for clutch wear which would push the slave cylinder back.

    Chas

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    It seems to me if the clutch, collar and fork and slave cylinder are all from a 280Z ( these have been confirmed) the clutch should work. I always install 240Z clutches in my 4 and 5 speed transmissions, so I use the collar, fork, pressure plate/disc, and slave cylinder from the 240Z with the ability to adjust. I've never installed a 280Z clutch, but with no hole for the plunger rod to go through the fork, there is obviosly no adjustment. From what I understand, awconroy is saying with all his 280Z clutch parts assembled, the fork arm still has an inch or so of play between the end of the plunger rod and the contact dimple in the fork arm. I suggest that he drill a hole in the center of the dimple so an early 240Z slave cylinder could be used to give you adjustment to take up the slack ( I set mine at 1/8 inches clearance). That being said, he needs to drill a hole slightly larger than the slave plunger rod diameter in the clutch fork dimple and install a 240Z slave cylinder....you could then adjust the plunger rod to attain the 1/8 inch clearance that the FSM calls for. Still have no idea why his existing set up doesn't work. Make sense?

    Edited by Diseazd

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    I've got the opposite challenge! 1972 240z with a 1977 280z 5speed. I'm using the 280z clutch, pressure plate, collar, and non-adjustable slave. The clutch seems to disengage very quickly (within the first third of pedal travel). Basically I only have to push the clutch pedal down 2 inches and I fully disengage. The clutch doesn't seem like its slipping at all (4th at low speed, throttle floored and now slipping). Any thoughts on this one?

    One easy test you can do. You don't even have to have the car on stands. Reach under and push the clutch fork into the slave cylinder. You should be able to push it in about 10mm.

    This is not the clutch pedal free travel explained in the manual. This is the extra travel needed for clutch plate wear. You will probably find it has no play and the pressure plate is partially engaged.

    I would also check the clutch pedal adjustment while your at it. Make sure the return spring pulls the pedal back to the stop and the pedal has 10 to 15mm free travel.

    Chas

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    Hardway had similar problems with a replacement master and slave cylinder for his 240Z. It was the adjustable type. The master cylinder rod was clearly a lot shorter than the original. He took a photo to show the difference. See post #107 http://www.classiczcars.com/forums/open-s30-z-discussions/47863-lime-green-machine-restoration-thread-1972-240z-2.html

    Chas

    Edited by EuroDat

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    @diseazed: there is no gap between the slave pushrod and the dimple, they are in contact. however the slave cylinder and pushrod cannot move the fork far enough. i'm only getting about 1/2 of travel before the slave "runs out". it just doesnt have a long enough reach.

    @eurodat: i actually can push the fork forward and compress the slave. the car is disassembled and somewhere else at the moment, but i vaguely recalling that distance being a half inch or better.

    i called courtesy nissan again today and read the part number back to them. they confirmed that this is the correct slave cylinder.

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    I quickly checked mine since its now on stands in the garage while Im replacing fuel line insulators. The slave cylinder has its own internal spring which pushes it back out when you let it go.

    I can push the slave cylinder push rod in and measured it with a tape measure how far it came back out. It was 7 - 8mm. The stroke was about 33 - 34mm.

    If your getting more than 1/2" free travel that could be some of the problem, but it wont make up the 35mm stroke the manual states. Thats about 5mm plus the 12.5 (1/2") travel you have comes to about 18mm which is about half what it should be.

    Is the clutch pedal free travel adjusted according to the manual specs?

    And is the system free of air?

    Chas

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    i confirmed that the pedal height is set at 8 3/4 according to the fsm

    the master cyl connecting rod is almost maxed out (just a few threads left)

    the pedal is contacting the bumper when not depressed.

    the line was completely drained, cleaned, refilled, then bled several times. then bled a few more.

    i did not check the pedal free-play adjustment though.

    giving serious consideration to buying a bench grinder and some roundbar and just making a longer pushrod.

    Edited by awconroy

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    I give up......seems like it's got to be in the master cylinder or a bleed problem......you've already tried two slave cylinders. What else could it be?

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    my suspicion is that everything is working as designed, but the current iteration of slave cylinders available for the 280z is the wrong design. (wrong pushrod, wrong bore, or maybe even offset mounting points). but short of buying one from every vendor and manufacturer i'm unable to find one that will work, so i'm going with your original suggestion.

    swap out the fork and slave for the adjustable 240 version and move on to the next problem.

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    swap out the fork and slave for the adjustable 240 version and move on to the next problem.

    I don't thick that will fix your problem. It might help a bit, but you could take all the free play out of the slave cylinder. That would mean the throw out bearing is pushing constantly against the pressure plate and it could cause it to slip.

    There must be something wrong with the diameter ratio master/slave being slave bore too big maybe.

    To make it adjustable, all you need is a long 5/16" bolt, a cap nut (thread tapped through it) and drill a hole in your fork.

    Chas

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    There are only two basic things you need to work with on the clutch hydraulic system - starting point and travel. The travel is determined by how the master cylinder's movement is transferred to the slave cylinder. The starting point is determine by the mechanical components. I don't know the spec. on travel but the posts above suggest it's about 35 mm or 1 3/8". If you're only seeing 1/2" of travel, it's either because the rod from the pedal to the master cylinder is moving without pushing the master cylinder piston, or the master cylinder piston is moving without pushing fluid. The slave cylinder is self-adjusting due to the internal spring, so it's not really an issue unless it's leaking.

    I left some detail out but that would be my basic starting point. To reiterate - if the slave cylinder is not leaking, it's not your problem. It only responds to the fluid being pushed in to it. If your not getting full travel, it's because the mechanical linkage is not adjusted correctly or the master cylinder is leaking internally.

    Blue must have been having a bad day. He seems yo be ignoring the fact that the specs. that the Asian companies use are set by the their "Western" company contractual counterparts. In other words, if your "Made in China" part has problems it's because your American company is making profit at your expense. There are many many high quality products made in Asia. Nest time you're looking at your fantastic picture quality big screen TV, amazed at today's' modern technology, look at where it was made. Probably China.

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    Zed....What you just said makes a lot of sense....If the pressure plate, collar, arm and slave cylinder are all 280z stuff, the system should work. The one thing that is a question mark is why is the slave cylinder linkage not moving enough? The only thing left is the clutch master cylinder. If the distance pushed on the piston in the M/C isn't enough to push the needed fluid to push the piston in the slave cylinder, it would be possible that the M/C is wrong, or that there is air in the system.....make sense? He's confirmed measurements are correct on pressure plate and collar, and has tried two different slave cylinders. If the push rod in the slave cylinder is touching the clutch arm now, then an adjustable 240Z slave cylinder isn't going to give you a longer push than what you have now. Awconroy.....Are you sure the clutch master cylinder is correct? You said it was bled....try it again. What else could it be?

    Edited by Diseazd

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    the mc was not leaking so i did not replace it. it was working prior to replacing the clutch and slave.

    it seems the only way to test re-bleeding the lines or replacing the master is to put it all back together (and hope it doesnt have to come out again).

    my current thought is that the slave pushrod is too short, allowing the slave piston to advance part way through cylinder before i even step on the pedal. it is effecively self-adjusting like it is supposed to, but for the wrong reason.

    @diseazed: the car and the clutch parts are still sitting on chuck's frame alignment rig, and i dont think i can leave it there too much longer. i need to present him a definate fix, or at least a permanent work-around.

    Edited by awconroy

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    Awconroy.....Sorry...I'm stumped....it's possible I guess that the pushrod is too short. I'm not familiar with the 280 slave cylinder....guess the piston is spring loaded to allow for auto adjustment. You could use the early slave cylinder with adjustment....it may or may not solve your problem. You could order a early slave cylinder and clutch fork. Give it a try....at least you'll know the travel of the slave cylinder piston should be right

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    well, before we all start blaming a nation of several billion people for my clutch problems...this slave cylinder was purchased from Courtesy Nissan.

    I also bought one from Arizona Z and it was identical.

    Not blaming, just stating facts.... I know a little about Chinese manufacturing..... and their products get into many supply chains sadly.

    EDIT See next post for possible solution

    Edited by Blue

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    I re-read your post and the "push rod on the master is fully extended" could be the culprit. You may have reduced the master's stroke.

    Think of the plunger in the master; for it to give maximum stroke, that plunger has to be back towards the firewall as a starting point.... this frame of reference may help.

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    I think I would start all over and begin with adjusting the pedal travel, make sure hats right then move to the slave cylinder.

    Like Blue said, if the master cylinder is not returning completly, it could be all your troubles there.

    Then check the free travel on the slave push rod and make a new one or use the original if its the better length. Just make sure you have between 5 to 10mm to allow for clutch plate wear.

    Chas

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    so for the sake of moving along and not having to drop the transmission a third time, i'll take the "belt and suspenders" approach.

    • replace the fork and slave with an adjustable 240 version (just in case)
    • re-bleed the slave
    • check the master linkage,
    • adjust the slave again if needed.

    surely something will come of doing all three.

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