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 Post subject: New clutch adjustment
PostPosted: Sat Apr 08, 2017 11:03 am 
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Joined: Wed Apr 09, 2008 5:53 pm
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Location: CT
I'm embroiled in an off-screen discussion about adjusting a new clutch on a 240Z. I used to adjust the clutch slave cylinder so often on my old '70 car that I can still close my eyes and picture the procedure. The "sweet spot" was so narrow, I painted the adjusting rod with red nail polish to tell me precisely where to adjust it after fluid swaps.

This discussion involves an old 240, armed with a newer ZX 5 spd gearbox. All my instructions about carefully adjusting the slave cylinder are moot and void, because apparently Nissan changed the clutch slave cylinder to a non-adjustable model for the ZX gearbox??

That would require all adjustments to be made at the Master Cylinder actuation rod, up under the dash above the pedal. Anybody have any first-hand experience with that? The new clutch slips severely and won't propel the car. I don't have a 280Z or ZX manual and no experience working on that newer slave cylinder system. Any input (even guesses) are welcome.

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PostPosted: Sat Apr 08, 2017 5:05 pm 
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As you thought, the adjustment for the clutch IS above the clutch pedal. With the clutch pedal up against the pedal stopper/clutch switch, take a measurement from the clutch pedal pad to the dash floor panel. Write that measurement down on a piece of paper. Slowly depress the pedal by hand, maybe 1/8", until it actually makes contact with the push rod that's going to the master cylinder. Hold the pedal at that location while measuring the distance, once again, from the face of the clutch pedal pad to the dash floor panel. The difference between the two measurements (pedal free play) should be 1-3 mm (0.04 -0.12 in). That's between 1/16" - 1/8" max.

The first (initial) pedal height measurement (when up against the pedal stop) should be between 195-205 mm (7.68 - 8.07 in) according to my 1985ZX Factory Service Manual for my 5 speed. It might be different on the 240, but shouldn't make a difference as long as the free play specs remain the constant. If adjustments have to be made you'll have to loosen the locking nut on the end of the push rod and turn the "U" connector, that has to be disconnected from the brake arm, to make the necessary adjustments.

This job is a little rough on the back and butt. Please use your red nail polish or a piece of painters tape to mark the present location on the threaded rod, just in case my instructions are way, way off. Good luck. :thumbs_up:

I would have guessed pink nail polish for you. lol. :P

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PostPosted: Sat Apr 08, 2017 5:36 pm 
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Thanks buddy ~ I'll pass that along. If it had the old 240 slave cylinder, he could just back the adjusting rod out a little to let the clutch grip more, but that's not an option here, obviously.

They were all out of pink nail polish; they said you bought it all the previous day. 8)

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PostPosted: Sun Apr 09, 2017 10:24 pm 
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Location: Ansonia, CT
Frank,

I ran into this working on Kevin's 240Z which had the 5 speed installed. Have you verified that you have the right slave cylinder, fork and throw-out bearing for THAT transmission? What puzzles me is that you say the clutch slips. As you know, if the clutch is released all the way without any hydraulic pressure to the slave, it should not slip at all with the non-adjustable slave. Have you checked that? It may be the clutch is slipping mechanically due to a misapplied part :roll: Just a thought.

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PostPosted: Mon Apr 10, 2017 10:47 am 
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Good input John, thanks. You are of course completely correct; without hydraulic pressure on the clutch, the plate should be in full contact with the pressure plate. I undrstnd the system is fully charged and bled, but the clutch spins almost freely.

The frustrating part of this issue is that I'm about 1,000 miles away from the car and am trying to help by remote control. The car is in the shop of a professional custom car builder who put it all together but now can't figure out why the clutch slips.

It's a member's magnificent hi-dollar 240 with a 5spd ZX gearbox and everything new, including a new clutch. The car has just been reassembled from a 3-yr-long, billion-dollar 3.1L rebuild with totally custom interior, exterior, paint and about 300hp. It's never driven a foot and is finally finished and ready to make its debut, but now refuses to move because the clutch slips.

I'm thinking it has the newer 5spd non-adjustable slave cylinder. The newer ZX cars depended upon making all the adjustments at the pedals, but the older 240s didn't have that capability, so it looks like there's no full-range adjustment available at either the old pedals or the new slave cylinder.

I'm thinking the solution might be to install an old 240 adjustable clutch slave cylinder on the newer 5spd, so you still have means of adjusting the clutch to where you want it? How did you resolve Kevin's issue?

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PostPosted: Mon Apr 10, 2017 9:02 pm 
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Well, my CRS is acting up again so I will have to check with Kevin tomorrow to confirm, but as I recall, when we tried replacing his failed slave with a new 240Z slave on his 5 speed tranny it would not install correctly as it kept pushing in on the clutch release fork no matter how it was adjusted. We then realized that we needed the different, non-adjustable slave which we eventually got to work after adusting the master push rod.

:? But again, you mentioned the system is charged and bled and the clutch is spinning freely. This makes me believe you have the wrong slave or throwout bearing installed OR that you have the wrong throwout bearing carrier for that tranny. That one bit me many years ago on my rebuild.

Boy, that car sounds awesome. Any pictures?

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PostPosted: Tue Apr 11, 2017 4:55 am 
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I've seen many pics of it an it's spectacular; electric windows, complex Comm/Nav system, Mercedes silver and grey paint, no external chrome, bumperless, custom seats, wheel and gauges, soundproofed interior and that maxed-out 3.1L injected engine.

If only we could make it roll!!! :lol:

It will debut here as soon as it comes out of the shop under its own power and gets shined up.

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PostPosted: Mon May 01, 2017 5:40 pm 
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What happened with this issue? Any updates?

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PostPosted: Mon May 01, 2017 7:09 pm 
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Here ~ I found the car in our Member Rides gallery:

http://www.ctzcc.com/cgi-bin/albums.pl? ... es.mcmahon

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PostPosted: Mon May 01, 2017 8:48 pm 
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No. No. No. Gallery photos are "past" and I'm more interested in "present". Was the slipping clutch problem resolved? What resolved the problem? Throw out bearing, slave cylinder, master cylinder? None of these? I sure hope that it WAS resolved and the car is up and running. :shock: :?

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PostPosted: Mon May 01, 2017 9:49 pm 
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I've asked for an update. I passed along all the info we gathered and suggested his mechanic buy an old Series-1 adjustable slave cylinder to fit on his 5spd ZX gearbox like I have on my car.

Strangely coincidental is that Big Al has just refitted his Li'l Red with a new throwout bearing and now can't make the clutch disconnect, either. Because he, too, has an early Z (where all the clutch adjustment relies on the slave cylinder) and a new 1978 ZX gearbox, a non-adjustable clutch slave cylinder is fitted (which relies upon adjustment at the pedals) so he effectively has no way to make adjustments. BUT ~ he just learned there are two size throwout bearings and he bought the smaller one. He has ordered the "fatter" bearing and an adjustable Series-1 slave cylinder and expects either or both those improvements to cure the problem.

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PostPosted: Mon May 01, 2017 10:25 pm 
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I will say a prayer to the Z gods for a final resolution to these clutch issues and an end to the human suffering that is being felt by these owners.
Maybe it's just a sign... that we shouldn't be messing around and "frankensteining" Z's? :idea: :?: :| :shock: :twisted: ?

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PostPosted: Tue May 02, 2017 9:52 am 
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Ah, Howard makes a good point, which is one reason I try to keep my car "mostly" stock. :roll:

It seems that every time you try to do an upgrade on a car, there is always a compromise encountered. Either replacement parts are harder to find, installing upgraded parts that will work with the upgrade set-up but which may not work well with other original OEM equiped car parts, access, interference, serviceablity, and the list goes on. Those of us that have upgraded our cars know this all too well. It makes you think sometimes that the original design may have had it's merrits! The same holds true when doing a tranny swap. As we know, there are additional items that will need to be swapped out to make it work with the rest of the car. I guess it's the price you pay for performance over practicality.

Frank, you mentioned Big Al experienced an issue with his throwout bearing install recently. This is what I was trying to point out in my earlier post as I still think that the subject car we are talking about had the wrong throwout bearing "collar" installed. This collar length differs between 70-74 Z's and those made from 75-83. The clutch will slip (be completly disengaged) if it is installed with the longer throwout collar which has NOTHING to do with the slave cylinder type. I know this from experience when I rebuilt my 4 speed tranny. The slave cylinder would be a separate issue and yes, it too must be compatible with the master and tranny as well.

Good subject for discussion tomorrow night? :wink:

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PostPosted: Tue May 02, 2017 10:43 am 
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If upgraded your old 240 transmission you need the bigger sleeve. If it all worked once and now it don't: A new master cylinder can have a different length rod, you need the long hex nut to extend the shaft, threads go both direction for adjustment. If you changed the slave cylinder, physical look and see if they are the same length, sometimes you have to switch the rods if you can. I have the old 5-speed installed, with the adjustable slave cylinder, and the fork has the hole in it unlike the other forks. then the bleeding procedure: By using the bottle method with hose on bleeder is the no fail way to know all the air is out, when no more bubbles. As far as clutch adjustment, should have some free play at the pedal to master side, can't be tight or cutch will not fully disengage. Another factor not to forget is week fingers on the cover if it can't go into gear easy and seems like air in the system. Not common, and usually old.


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Last edited by Paul on Tue May 02, 2017 9:46 pm, edited 1 time in total.
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PostPosted: Tue May 02, 2017 2:16 pm 
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Wow! :? I don't claim to know too much about transmissions and clutches, but.... the "bleeding" sequence of RR, LR, RF and LF sounds more like "brake" bleeding instructions. :shock: :roll: :wink: Since when can you bleed a transmission from its four corners? :P Sounds VERY unique. :mrgreen:

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