Clutch Hell-p

[Bishopsrock]

Ok - 2 years & 6 months doing this conversion (and a few other mods) - I did the wiring myself and it started first time:-D - but I still can't drive it because of my clutch - Gutted!!!

 

My engine is a R33GTR and the guys who sold me the gearbox said that they though it 'may' be out of an R34DET.

 

Sorry if I don't make 100% sense here but i'm dead tired - I will do my best though.

 

I could not get the car into gear. I thought that my clutch was stuck on. So I did the usual - but no joy. Here are pics of my slave and master cylinder so as to set the scene.

 

 

 

 

 

I bled the system with a friend pumping the pedal - made no difference. So, I made an improvisation to the slave cylinder to take all the slack out of the plunger and the arm. I thought it would at least get me going. Below is a pic of my modification:-

 

 

After giving the plunger loads of extra forward travel by extending its length, I could only get it into gear if I start the car in gear. Even with full depression of the pedal, the clutch was not fully disengaged and the car needed a firm foot on the brake to stop it moving forward.

 

I had been reading everything I could about clutches on HybridZ but there is not much that I could find on our RB forum and other forums were talking about different setups.

 

I didn't put the box and engine together myself and I used a secondhand clutch - bad move I know but I thought that I would probably burn my first clutch out quickly anyway. So I decided that the problem was most likely with the clutch. Most, most likely because the pressure plate was on the wrong way round or something! Soo I got a brand new clutch, got the first aid kit ready and pulled off my gearbox.

 

WTF - the clutch looked ok and was on the correct way round!!! Below are the pics - old next to the new:-

 

 

Next the clutch Plates:-

 

 

Just for completeness below is a pic of my clutch fork & release bearing:-

 

 

My problem is this - because the old clutch was fitted correctly and because I couldn't find anything wrong with it, I just know that when I put my gearbox back in tomorrow, that I am still going to have the same problem!!!

 

Please will you guys study these pics and see if its obvious to you why I cant get the clutch to fully disengage???

 

Thanks

[RB26powered74zcar]

You prolly have the wrong thickness throw out bearing collar.... that set up looks awfully thin.

[pirate87]

I was under the impression that the R34 RB25 transmission was a pull-type clutch...not that this solves your problem, but it may help you prove that what you were sold isn't an R34 tranny.

[Bishopsrock]

You prolly have the wrong thickness throw out bearing collar.... that set up looks awfully thin.

 

Thanks for helping,

 

Do you have a measurement for your collar or a spare that you could measure for me?

 

Cheers

[BirdmanZ]

Did you check the pivot ball on the transmission?

[Sam280Z]

What kind of clutch did you get? I have seen one case where a brand new ACT pressure plate was too thick (244mm L6 setup).

 

Another possibility is too much runout in the clutch disk.

 

Sam

[RB26powered74zcar]

Did you check the pivot ball on the transmission?

 

I didn't think of that one! I have never messed with the pivot before. Can the height be adjusted to make up for play between the the throw out and the fingers the throw out pushes against?

 

I'm assuming his problem is not enough leverage on the pivot arm, from the slave, when the clutch pedal is pushed in.....

[Slow_Old_Car]

You may need to shim up the pivot ball in the bell housing. Since your tranny is out, put a couple of washers under the pivot ball tower to bring it out 1/4" or so.

 

When you've re-assembled, if it still does not work, you may have run into a problem with the plunger rod on the clutch master itself.

 

I had this happen once and it had me pulling every part of the system apart for a week straight before i figured it out (cause everything was brand new)

 

Before you re-assemble, get under your dash, with a sharpie mark on the plunger pushrod mark where it sits against the casing grommet of the master cylinder.

 

Then grab the clutch pedal and press it all the way till it his the stopper, and mark that position on the plunger rod at the master cylinder grommet.

 

Now take the cotter pin out so that the plunger falls away from the clutch pedal arm. Go remove the bolts and remove the clutch master. Set it on a work bench or the likes, and depress the plunger 100%, if your line that you marked with the clutch arm doing the depression disappears inside the clutch master casing, then you are not getting full pressure to the clutch slave. Thus screwwing yourself out of movement length.

 

In the end, with parts being hard to get, my solution was to ad 1/2" of bar into the plunger rod itself via welding it inline. I reassembled, re-bled, and presto it worked.

[BirdmanZ]

I wonder if your clutch master cylinder is the same size as the US cars. My clutch disengages just a bit before the pedal hits the floor and that's with the rod adjusted all the way out. It's enough for full disengagement but I'd like it to be more in the middle of the pedal's travel. I bought a 7/8 master cylinder from Wilwood that should help out by moving more fluid. If your pivot ball is OK and you have no leaks in the hydraulic system, I would look into getting a larger clutch master cylinder. I believe the one I got was around 90usd.

 

BTW, I wouldn't go shimming up the pivot ball, it could cause the throw out bearing to ride on the pressure plate constantly and wear it out prematurely.

 

Brandon

[Bishopsrock]

Thanks for that guys,

 

I have today been to the breakers yard and looked at a new R33 RB25DET transmission. I couldn't believe it but it had exactly the same size of carrier as I have and the fork looked the same as well. So no one has switched the RB parts for some ones from another model that don't work.

 

I then went on a mad transmission hunt - these guys just couldn't get the idea that I was looking for a longer throw out bearing carrier. I can't believe it but I was lucky (for a change) and found one!

 

I pressed the new bearing off the original carrier and onto my lucky find which is about 10mm longer.

 

Also, I had a chat with RB Motorsport here in the UK and Rod told me that the Nismo slave cylinder is a thinner bore and so would help if all else fails.

 

So thats what I am on with now - but I am having difficulty getting the box to go back in on my own - maybe using a socket as a clutch alignement tool wasn't such a good idea!!! I will keep you posted but its definately not coming off again!

 

Has anyone looked at the differences between the standard cylinder and the NISMO one?

 

Thanks for the idea about the master cylinder Slow_Old_Car. At 5/8 it is the right size but if the travel is less than it could be then this could also buy me a bit more push.

 

I didn't want to shim up the pivot because of the way that the arm attaches to it - once I get this back in I don't want any risk that I might have to take it out again.

 

Anyway I just need to get the box into the flywheel to find out if my new clutch & extra 10mm on the throw out collar does the trick.

[RB26powered74zcar]

Alot of clutch company's provide their own new T/O bearing already attached to the new collar, because their finished height of the pressure plate fingers are different than a stock clutch, so again, that may indeed solve your problem by getting a 10mm taller collar....

 

In that picture you provided above, showing the old and new pressure plate side by side, you see where the T/O bearing has made its mark on the old one, where it engages against the fingers?...... just for $hit$ and giggles, place both pressure plates on a smooth surface, then can you grab a tape measure and stick it into the hole in the center of each pressure plate, and measure from the surface they are laying on, up to the fingers where the T/O presses on them, and see if you get the same distance on the old and new pressure plate... just curious...

[BirdmanZ]

I believe the Nismo slave cylinder is a larger bore than the stock one. It's used for clutches with a much stiffer pressure plate to keep the pedal from being really hard to push. Others refer to it as a Nismo big operating cylinder.

[cheftrd]

The newer Nismo slave cylinders have a larger bore. Up to 13/16 from 3/4. It reduces pedal pressure by 14%, but increases travel required to release the clutch.

[Bishopsrock]

Hi Guys,

 

Thanks for all that info and help - this forum really is amazing.

 

I struggled like hell to get my tranny to go go back in and eventually did it with my mate who is built like a Bull Elephant at the front and me holding on to the rear suspension and pushing forward with both feet on the tail end. It would be fair to say that this is not the most easy of clutches to change.

 

The 10mm longer collar definately helped and it feels like the throw out bearing just clears the cover with it on.

 

But after I put everything back together and started it up I still could not get it into gear!

 

So I put my original spacer back in but then I couldnt get the clutch to bite and had no drive. Next, I put a small 4mm thick bolt beneath the cylinder rod and hey presto, I had a clutch.

 

Its still not right though because my throw out bearing is probably in contact with the cover now.

 

All I can do next is get a new master and a new slave - then at least I will know that everything else is spot on.

 

If anyone has any new ideas please let me know as i'm running out?

 

Anyway onto the juicy bit - I took it for a short spin. I have driven a couple of Ferraris, my business partner has an Audi RS6 and my mate has got one of the last Lotus Esprit Turbos ever made but my simple 240z was unreal. It came on boost and I got ground rush going forward! It is just so quick its utterly amazing and thats without any mods!!! Right now I know my conversion is worth every penny and has definately been worth the wait.

 

Cheers

[getoffmyinternet]

I know I'm beating a dead horse, but I had one inquiry because mine is like birmanz and I have the 3/4 slave as well. I hear that the nismo slave being larger makes easier but longer travel? That's the last thing I need, however I don't want to overstiffen the clutch action in reducing the travel with a smaller slave. Does getting a larger master make the action stiffer as well, or just push more fluid and fix both problems?

[Mike Rowe]

I am trying to sort my slave cylinders out at the moment so this thread is very timely.

The slave cylinder that came with my R32 GTR halfcut is I think for a push clutch and is the same as the one in your photo above. I could get it to line up with the pull clutch (my gearbox is supposed to be R34 RB25DET) but the bleed and feed in were between the gearbox and the slave in other words pointing towards the gearbox which obviously isnt right.(see first photo no bleed or inlet line can be seen) The engine is to the right of the photo so bolts are in a different position to yours

Today I went to Nissan and brought a brand new R34 RB25DET slave cylinder (Aust$63) and it is twice as long which surprised me but at least is facing the correct way (see attached photo 4).

I havent fitted it to the gearbox yet but will report back.

What I can say though is:

(1) Your slave cylinder and gearbox photo shows that the gearbox is not an R34

(2) On my GTR halfcut the clutch pedal and master is hooked up to a small booster like on your brakes, which is obviously to lighten the heavy clutch that you are experiencing. I am now wondering whether to try and fit the GTR master and booster?

[Careless]

check your input shaft spigot and pilot bushing for abnormal wear while you're at it if you havent!