# Clutch adjustment a definitive guide



## adamsaiyad (Aug 23, 2006)

Hello members, i have been meaning to ask this publically and it would mean alot to me and im sure other members.
What is the correct way to adjust a pull clutch system on Gtr's
I have been told many a time that its so important that its set correctly ?
So how does one set the clutch correctly whats the correct procedure.
I see people talking about end float procedures and alot of other posts about what i should assume is even more complicated information.
But there is nothing on clutch adjustment and how it should be done.
Can any one help here .
Maybe Rob cares to shed some light as he has recommended it to me a few times as well.
????????????????????????????????????????????


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## Andy W (Dec 31, 2005)

you need to have free play between the release arm and the push rod in the slave, you can get the adjustment from the pedal/pushrod by slackening off the preload on the master cylinder

too much preload will make the push rod press the release arm pushing or pulling(depending on clutch type) the release bearing and taking up the end float the crank has


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## adamsaiyad (Aug 23, 2006)

Andy thankyou for that information.
There seems to be alot of secretive information regarding clutches eating engines etc like mine for example.
Now the end float plays a part on the crank and when there is no end float because of a clutch improperly adjusted it can eat up thrust washers?
But how now does a engine survive the daily changing of gears and sometimes at rpms close to 7 or 8 thousand rpm ?
Yes its for a few seconds and presumably the crank glides on the bearing but in a 60 000kms engine it would have touched a fair amount of times im certain ?


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## frostmotorsport (Aug 10, 2007)

more to the point - how often do people sit at the lights with their foot on the clutch?? I would have thought if this were the case (re: endfloat vs clutch adjustment) we would see a lot more failures in all types of motors... not just RB's


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## mattysupra (Oct 31, 2008)

frostmotorsport said:


> more to the point - how often do people sit at the lights with their foot on the clutch?? I would have thought if this were the case (re: endfloat vs clutch adjustment) we would see a lot more failures in all types of motors... not just RB's


Thats what i was thinking!


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## mattysupra (Oct 31, 2008)

More so, the 34 is pull so pulling the pressure away from the crank? 

With 32/33 they are always pushing against the crank? So i take it that 32/33 suffer more with this issue?


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## Andy W (Dec 31, 2005)

if you ride the pedal, or start the engine with the pedal down it causes wear & yes sitting at the lights with your foot down causes wear


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## mattysupra (Oct 31, 2008)

Andy W said:


> if you ride the pedal, or start the engine with the pedal down it causes wear & yes sitting at the lights with your foot down causes wear


on both push + pull type? 

How come on some cars you cant start the car unless you dip the clutch? Is it down to a different design maybe?


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## Andy W (Dec 31, 2005)

both types

about the only one i know is the chrysler Neon, its just a switch that causes the non start in case you are to thick to check its in gear, after all you did buy a Neon so something must be wrong :chuckle:


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## mattysupra (Oct 31, 2008)

Andy W said:


> both types
> 
> about the only one i know is the chrysler Neon, its just a switch that causes the non start in case you are to thick to check its in gear, after all you did buy a Neon so something must be wrong :chuckle:


My evo wouldn't start unless you press the clutch pedal in?


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## deep_space (Jan 27, 2010)

Nor will some bmw's or volvo's. Surely if the clutch wasn't adjusted to the extent of it being able to wear the thrust bearings out. Then the clutch would slip under any power you put through.


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## Andy W (Dec 31, 2005)

If the crank is pulled or pushed against the thrust bearing all the time it will start to wear out the bearing 
with a twin or tripple plate fitted it could still have preload and not slip. the release arm must have a small amount of free play from the push rod in the slave.


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## mattysupra (Oct 31, 2008)

Andy W said:


> If the crank is pulled or pushed against the thrust bearing all the time it will start to wear out the bearing
> with a twin or tripple plate fitted it could still have preload and not slip. the release arm must have a small amount of free play from the push rod in the slave.


Get what you mean, a bit flappy for a couple of mm when pulled/pushed by hand ?

Is it just RB's that suffer with this? I always used to hold me clutch pedel down on previous cars van, but on my RB (after reading about a simular issue) i always select neutral as soon as i can. 

On previous motors that i have put well over 100000 miles on i have held the clutch down at all times as i was led to belive this is better 
How come these other vehicles have not had crank issues?


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## adamsaiyad (Aug 23, 2006)

when i last left this post it was sitting at 3 posts firm .... go to sleep and wake up and find a story developing, its good to see people have taken a interest.
As i have asked the question i will comment on some of the comments lol.
Firstly that clutch depression to start the car is a factory switch that can be bridged in most cars.
The other thing is imagine a bearing needs oil to lube and glide etc so in the case of the thrust washer the oil pump lubes the thrust and these thrusts last up to 250 000kms on other cars subarus and nissans included .
So how is it possible that in my case after 1000kms i wrecked an engine supposedly because of a badly adjusted clutch ?
Understandable if the car had done 100 000kms of bad clutch adjustment lol.
So in saying all of this i would suggest matty and other member disconnect the clutch engagment option for starter engagement, its a switch on the clutch pedal that has two wires that need to be bridged soldered or paperclip can do the trick.
This will mean that which ever the car maybe that had this wont be loading the thrust washers wether it be a push or pull option, during the harshest time ..... during a cold non lubbed starting process.
This i think might have done more damage then any good at all on my engine.


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## adamsaiyad (Aug 23, 2006)

Ps on another point, the slippage should occur if the clutch is a single.
And should also occur if the clutch adjustment isnt correct this has happened to me before in the past when i was experimenting with the pull clutch of a wrx .
Drove it for ages with it incorrectly adjusted and never ran bearings or had problems of crank walk.
Eventually corrected the problem and car still running .


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## deep_space (Jan 27, 2010)

I know of a car that shat itself after less than 10 miles. This was blamed on clutch adjustment. It had a multiplate clutch and you could hear clutch jingle when released. This was also the same clutch as used before the engine was changed. And it ran fine before. Surely nothing would have needed adjusting. Also does the clutch hydraulic system actually suck the rod back into the slave, or is it just pressure of the arm pushing the rod back in. If it does suck the rod back in why do os giken sell a kit with a small spring to pull the release arm back


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## adamsaiyad (Aug 23, 2006)

interesting read once again and yes the hydraulic clutch will pull the slave cylinder pin back.
But you must remember a hydraulic clutch has one acting force and thats to pull or push .... not push then pull the clutch back into shape per say.
So with that being said its up to the fingers on the clutch pressure plate to pull the arm and push to pin some what into position.
Os giken probably put that system in place because of the free play aspect the clutch probably had alot and the pin would hang a bit out of shape so the spring was added to keep it in place.

So this clutch adjustment still seems a mystery, and broken engines also seem to point to that as being a problem but is this really true ?


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## chippy (Mar 14, 2008)

porly adjusted cluch = blown engine
i dont think so
me thinks yet another excuse lol


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## adamsaiyad (Aug 23, 2006)

it might have been oil from the modine unit that was from the first engine failure that caused this problem ?
Though i posted a question on it and no one could quite answer ?
One person did say the modine unit gets oil before the filter and therefore couldnt have been dirty etc but i beg to differ i have seen a few guys change them on a rebuild and thats just another trick in the book for prevention is better the cure.... lol


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## adamsaiyad (Aug 23, 2006)

No other comments


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## frostmotorsport (Aug 10, 2007)

just one in regard to the slave cylinder being "pulled" back - I think you will find that the clutch pedal has a spring on it, which forces the pedal to the top of its movement when you take your foot off and the pressure plate is all the way out (or in). This in turn pulls the piston out of the master cyl all the way, and hydraulics being what they are, this will naturally pull the slave all the way back.


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## R.I.P.S NZ (May 7, 2004)

I have some info from ACL which confirms it is quite common and very possible to destroy a set of thrust bearings very quickly when the clutch is not adjusted correctly.

There are other causes as well but all relate to excessive forward pressure on the crankshaft overloading the thrust face of the center main bearing.

Rob


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## blue34 (Jul 28, 2005)

I have also seen 3 different length thrust bearing carriers from 33 and 34 GTRs, for different gearbox / clutch combinations. Use of the wrong length bearing carrier can even result in the clutch fork touching the edge of the clutch cover, particularly on triple plate clutches and might also make it difficult to get the correct clearances.

The slave cylinder operating rod must be of the correct length to match the slave cylinder piston movement ie the piston has enough movement back and forth to operate the clutch and allow for a small amount of free play.

Clutch hydraulic seals only work in one direction there is therefore minimal "suck" back it relies on the clutch springs to push the fluid back when the clutch is released. Without the clutch fork in place two pumps of the clutch will usually result in the piston popping out of the slave cylinder.

An incorrectly adjusted clutch without free play will result in the release bearing being tight against the clutch, permanently spinning the bearing. This will result in the clutch release bearing wearing out prematurely.

A clutch so tightly adjusted that it can apply enough pressure to wear out a properly fitted crank thrust bearing in a very short time ie a few miles, yet still function normally i.e. have correct pedal movement and not slip seems quite unlikely to me unless there is incompatibility between some components.

Other reasons might include an incompatibility between a gearbox input shaft and a crankshaft spigot bush, if the input shaft cannot slide freely into the rear of the crankshaft this would cause a very high crankshaft rear load when the gearbox is bolted up.

A common cause of engine failure ater a rebuild is swarf inside a crank if it's re-used. It's very difficult to be 100% percent sure a crank is clean as the main crank oilway casting holes are plugged during manufacture.

I experienced an engine that failed after less than 1000 miles, it was nothing to do with the engine asembly itself It was due to a missing 10p "O" ring where the oil pick up pipe bolted to the block which allowed the oil pump to draw air in. (not an RB).


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## bessas (Jan 23, 2011)

Hi can any one help i need a clutch for my r33 gtr but dont know what is available and where can i get it.
A clutch that can hold up to 400 or 450 bhp as that is what im aiming to take my skyline to


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## R.I.P.S NZ (May 7, 2004)

Info from ACL:

Crankshaft thrust face failures can occur due to a number of causes. Wear
can (in some instances) be so severe that there is little evidence that
remain for analysis after the event.

Thrust faces could easily wear in excess of .040" in the first 7 to 8 miles
as recorded in some cases. Some possible causes of failures are listed
below.

1) Crankshaft thrust surface finish - it is important to have the correct
surface finish on the thrust faces of the crankshaft. Maximum roughness
should not exceed 0.4 micrometers (15 micro-inches). Also important is
finishing the thrust surface by polishing, so that any remains of
"microscopic fuzz" left over from the grinding procedure is removed. If the
surface finish is not correct the shaft surface can quickly tear up a
bearing thrust face leading to lubrication breakdown and premature failure.

2) Insufficient or lack of oil supply to main bearing and thrust faces
during initial start up.

3) Squareness of the crankshaft thrust faces. 0.020 mm (0.00075") maximum
or the crankshaft will make a point contact with the bearing thrust face,
causing an overloading situation rather than an evenly distributed load.

4) Maladjustment of the clutch so there is no free play - this can result
in a constant load on the thrust face, resulting in lubrication breakdown,
overheating and subsequent thrust failure.

5) Excessive clutch load - lubrication breakdown of the boundary oil film
and overloading of the bearing thrust face material, overheating and
subsequent thrust wear.

6) Incorrect alignment/ installation of the pilot bushing/spigot bearing
and/or gearbox input shaft.


Rob


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## pdtuning (Nov 7, 2009)

Having trouble with my release bearing pushing against my clutch, when the pedal is fully out
Here's the link
http://www.gtr.co.uk/forum/147215-tripple-clutch-slipping-boost.html


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## REDWOOD (Apr 21, 2010)

I replaced my triple plate os giken clutch (push type) and no matter what I tried I could not get enough movement in the slave cylinder to dissengage the clutch. I eventually gave up and adjusted the slave so it applied pressure on the pressure plate, it was the only way to get gears. So my release bearing has been applying plessure on the crank for a couple of years and over 2000 miles. Have I been lucky or is it a matter of time?


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## mattysupra (Oct 31, 2008)

REDWOOD said:


> I replaced my triple plate os giken clutch (push type) and no matter what I tried I could not get enough movement in the slave cylinder to dissengage the clutch. I eventually gave up and adjusted the slave so it applied pressure on the pressure plate, it was the only way to get gears. So my release bearing has been applying plessure on the crank for a couple of years and over 2000 miles. Have I been lucky or is it a matter of time?




I too had this issue, however after taking the gearbox on and off 9 times i stuck a different clutch in there. 

When you say you changed your triple plate did you put new plates in there or a whole new clutch? 

And how did you adjust the slave to apply pressure all the time?


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## REDWOOD (Apr 21, 2010)

mattysupra said:


> I too had this issue, however after taking the gearbox on and off 9 times i stuck a different clutch in there.
> 
> When you say you changed your triple plate did you put new plates in there or a whole new clutch?
> 
> And how did you adjust the slave to apply pressure all the time?


Wow 9 times, that must have been fun!

I changed mine by myself on the floor with axle stands and a special jack I had made just for this job.

I changed the clutch plates, pressure plate and release bearing, basically everything except the flywheel. What I could not understand is that all I did was swap like for like but it just wouldn't work. I bought the car and the clutch didn't have much life left in it so I don't know how it was when new. 

I extended the slave rod by screwing the dome shaped "nut" all the way to the end until half the threads remained on the slave shaft. I then got a bolt with the same thread, cut the head off and screwed it in other end of the dome shaped nut. I then got some washers and placed them on a large nut and punched them in the centre with a bolt to make them dome shaped. I then adjusted the clutch using more or less washers on the end of the slave shaft.

I think as the clutch has worn, there is less pressure on the crank than when I changed it.


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## mattysupra (Oct 31, 2008)

REDWOOD said:


> Wow 9 times, that must have been fun!
> 
> I changed mine by myself on the floor with axle stands and a special jack I had made just for this job.
> 
> ...



I also started to do what you have mentioned above but then realised i would be putting pressure on the crank so decided not to go ahead. 

After taking the gearbox on and off 9 times i admitted defeat and installed a different clutch. 

The thing that is strange about mine tho is that the clutch that was in there was working fine, i removed it and then refitted the same clutch and it would not work any more? I know i fitted it correct as i originally installed it when it was new! 

I think i know why it dont work but i cant face taking the gearbox off again to test it and for it not to work again. 

In total i have had my gearbox on and off maybe 12 times in 1000 miles.


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## REDWOOD (Apr 21, 2010)

mattysupra said:


> I also started to do what you have mentioned above but then realised i would be putting pressure on the crank so decided not to go ahead.
> 
> After taking the gearbox on and off 9 times i admitted defeat and installed a different clutch.
> 
> ...


What do you think is the problem?

I concluded that there must be air in the slave cylinder hydraulics which I could not expel so could not get maximum movement.

Or the clutch kit was not designed properly ie it did not take into account the travel of the slave.

I have been driving without any problems for a while now and I reckon if I try to put everything back to standard it would work, as everything has bedded in by now.

The worst part of changing the clutch was lining up the 3 clutches even when using the fwd driveshaft.


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## mattysupra (Oct 31, 2008)

REDWOOD said:


> What do you think is the problem?
> 
> I concluded that there must be air in the slave cylinder hydraulics which I could not expel so could not get maximum movement.
> 
> ...


I think or should i say i know that the metal plates that run between the clutch discks are very slightly warped. All tho they was marked of which way around they went i had either fitted one of the plates the wrong way around from new and not noticed which has now caused me to put the clutch back in the correct way around and the warped plate is causing the issue. 

Basically in my clutch (triple carbon) i needed to keep the plates and clutches all the same way around and at the same angle they they came out (as in the mark on the edge of the metal plate is at 1 o'clock i needed to keep it at 1 o'clock ) 

I have had the clutch in a press and all types trying to figure out what is wrong and it needs about 1mm more movement on the pressure plate to release than the slave cylinder could provide. 

Basically if i skim 1 mm of the flywheel it will work, but then im scarred it will re bed in and i will have a slipping clutch as i just removed 1mm! 

I guess i could skim all the plates flat again but the removal of the tiny bit of materail may send them to thin and make them warp worse? 

What i need to do is keep trying different ways of putting the plates back in and keep trying it in the press untill it realeases at the correct amount of pressure and then stick it back in the car. (cant be arsed tho) lol


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## freakazoid3 (Jan 19, 2008)

^^Sounds like way to much hassle to try back on the car 

But you made me a bit scared now as I've got a HKS triple here ready to go on my R32 GTR with an R34 getrag gearbox. 
And I'm not wanting to do it more then once


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## blue34 (Jul 28, 2005)

mattysupra said:


> I think or should i say i know that the metal plates that run between the clutch discks are very slightly warped. All tho they was marked of which way around they went i had either fitted one of the plates the wrong way around from new and not noticed which has now caused me to put the clutch back in the correct way around and the warped plate is causing the issue.
> 
> Basically in my clutch (triple carbon) i needed to keep the plates and clutches all the same way around and at the same angle they they came out (as in the mark on the edge of the metal plate is at 1 o'clock i needed to keep it at 1 o'clock )
> 
> ...


Frome my earlier post:

And just to add - the fulcrum pin (the bolt with the domed head) that the clutch fork sits on can also be varied in length by width of the washer under it. That's another variable...

I have also seen 3 different length thrust bearing carriers from 33 and 34 GTRs, for different gearbox / clutch combinations. Use of the wrong length bearing carrier can even result in the clutch fork touching the edge of the clutch cover, particularly on triple plate clutches and might also make it difficult to get the correct clearances.

The slave cylinder operating rod must be of the correct length to match the slave cylinder piston movement ie the piston has enough movement back and forth to operate the clutch and allow for a small amount of free play.

Sounds to me like you might have the wrong combination of the above 3 options...


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## mattysupra (Oct 31, 2008)

blue34 said:


> Frome my earlier post:
> 
> And just to add - the fulcrum pin (the bolt with the domed head) that the clutch fork sits on can also be varied in length by width of the washer under it. That's another variable...
> 
> ...



Nope, not wrong combi. The clutch was fitted brand new by myself and done 1000 miles with no issues. I blew an engine and rebuilt it, i then refitted the same clutch and gearbox (gearbox was new 1000 miles as was the clutch) and it was dragging. 

Like i say i had the gearbox on and off 9 times trying to sort the problem. As i was using the same parts that came off there should not of been a issue but there was. 

In the time of the gearbox coming on and off i tried a different length pivot + bearing and was still the same. 

I was then thinking that maybe my new crank or something could have a issue so i tried a different clutch. The new clutch works fine as it should. But sadly it cant handle the power so needs to be changed for another triple plate. However the new clutch was good another to run the engine in and map the car on so im not in a rush but i really cant face taking that bloody gearbox off again~!


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## REDWOOD (Apr 21, 2010)

mattysupra said:


> I think or should i say i know that the metal plates that run between the clutch discks are very slightly warped. All tho they was marked of which way around they went i had either fitted one of the plates the wrong way around from new and not noticed which has now caused me to put the clutch back in the correct way around and the warped plate is causing the issue.
> 
> Basically in my clutch (triple carbon) i needed to keep the plates and clutches all the same way around and at the same angle they they came out (as in the mark on the edge of the metal plate is at 1 o'clock i needed to keep it at 1 o'clock )
> 
> ...


I agree that the warped plate will take up some of the movement of the slave so you don't get full release but I dont see how shaving 1mm off the flywheel will help.

The problem as I see it is that the travel of the slave rod is not enough to release the pressure plate, adjusting the thickness of the clutch or shaving the flywheel is just moving the fork back or forward. The fundamental problem of slave rod travel will not be addressed. 

Has anyone used a slave with more travel ie one with a smaller diameter piston?


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## mattysupra (Oct 31, 2008)

REDWOOD said:


> I agree that the warped plate will take up some of the movement of the slave so you don't get full release but I dont see how shaving 1mm off the flywheel will help.
> 
> The problem as I see it is that the travel of the slave rod is not enough to release the pressure plate, adjusting the thickness of the clutch or shaving the flywheel is just moving the fork back or forward. The fundamental problem of slave rod travel will not be addressed.
> 
> Has anyone used a slave with more travel ie one with a smaller diameter piston?


If i shave the flywheel i will need less pressure to release the clutch plates as they will be move more freely. 

For instance, when the carbon clutch wears and starts to slip you fit a 1mm shim (inside the clutch) to increase the clamping pressure again. BUT i should not need to do this hence i dont want to as i can see teh clutch starting to slip when it beds itself back in. 

As for your next question, i tried a standard and a nismo slave to try and fix the issue and a new master cylinder. If i was to fit a slave with more throw (i only need another 1mm) then it would of solved the problem. 

But am i know going to be putting to much force on the thrust bearings? I am in theroy giving more clamping force and needing to apply more pressure on the front of the clutch to make it release?


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