Clutch Slipping Since Rb25 G/box Conversion :(

[huddy]

ok

are rb20 / 25 / 26 clutches all interchangeable?

and is there something i've forgotten in the rb25 box conversion (possibly inside the bellhousing or something)?? it drives around but the clutch just slips under load!!!

...since i have done a rb25 gearbox conversion on my cefiro (rb20det) i have had issues with clutches -

firstly was a nismo gmax (2nd hand) but was working fine before conversion (blew the 20 box!!). since installing this rb25 gearbox had numerous problems getting it right - and the clutch not slipping...

NOW

i had a tilton twin plate fitted as the other clutch was slipping - and same again - minimal load / 0 boost / under 3000rpm and the clutch slips (running motor in so DEFINITELY no thrash/big load up)

had the box in and out changing things on it - changed the pivot ball to a longer one, as the clutch fork had play before and not even touching the slave cyl... but now the pin sits up on the fork nicely

cut the back of the carrier inside (i think thats what it was about 4mm) the bellhousing move it back a little as it was almost like the thrustbearing was constantly touching the fins (or front of the clutch)

the clutch pedal only has about 10-15% of the full pedal's worth that actually is being used to engage - disengage the clutch

rb25 box bolted straight up to rb20 motor - lengths were the same - gear lever comes out the transtunnel in the right spot etc...

WHAT THE HELL COULD IT BE?

[1400r]

please help Im the one who has to help pull the box out everytime

[Cubes]

Check its not leaking oil.

I had my clutch slip easily when my front input shaft seal was leaking/seeping.

I pulled off the clutch and it was a complete mess.

Replaced seal, no more slip.

But yours sounds extreme, so likely not related. :S

[dangerous_daveo]

Which slave cyl did you end up using?

[1400r]

used a 33 slave no oil leaks thanks cubes box has been out a few times

what would be the symptoms of a incorrect type of clutch being fitted i.e the whole push pull thing

I think maybe the last two clutches put in were a different type to what was required?

Ive heard you can convert them? read it in the hpi r34 build up

[Bl4cK32]

are rb20 / 25 / 26 clutches all interchangeable?

only rb20, rb25 series 1, and r32 gtr

had the box in and out changing things on it - changed the pivot ball to a longer one, as the clutch fork had play before and not even touching the slave cyl... but now the pin sits up on the fork nicely

that sounds like a problem there. From memory the slave should be touching the fork whithout pressure on the pedal. I cant remember if you can just turn the pin to make it longer to take up freeplay??

cut the back of the carrier inside (i think thats what it was about 4mm) the bellhousing move it back a little as it was almost like the thrustbearing was constantly touching the fins (or front of the clutch)

i think its supposed to be....

the clutch pedal only has about 10-15% of the full pedal's worth that actually is being used to engage -disengage the clutch

have you got under the dash to lenghten the master cylinder rod to adjust the pedal?

rb25 box bolted straight up to rb20 motor - lengths were the same - gear lever comes out the transtunnel in the right spot etc...

did you change bearing carrier over when you changed the clutches? make sure you have the right one in. This can stuff the clutch...

Edited May 13, 2006 by Bl4cK32

[huddy]

thanks for the info guys

BTW - it is a series 1 rb25 gearbox also so that should be ok.

and could it be possible that the master cylinder (changed to 33 slave cylinder) would need to be changed also?

Bl4ck 32

- so how can you tell what the clutch is meant for what type of motor?

- have changed to a longer pivot ball and slave pin was sitting on the fork not too much but but still applying some tension

- ok

- does this need to be changed with a standard clutch replacement also?

- the thrustbearings where changed previously with the old nismo gmax clutch, and it is still the same one - smaller than standard - that is being used on this tilton twin plate

thanks

-matt

[huddy]

anyone else have any ideas???

was either thinking of replacing with a stock rb20det clutch just to see if that drives ok - then it will tell us if its either the wrong clutch (the twin plate) for the rb20det / rb25det gearbox setup; OR its in the actual motor/box setup :S

[Cubes]

It appears you have fiddled with a couple of things that really shouldn't be fiddled with, as we do from time to time.

- have changed to a longer pivot ball and slave pin was sitting on the fork not too much but but still applying some tension

Return it to standard, run the standard fork, pivot ball and slave cylinder.

Standard everything.

- the thrustbearings where changed previously with the old nismo gmax clutch, and it is still the same one - smaller than standard - that is being used on this tilton twin plate

I believe this is where your problems stem from.

Get the correct thrustbearing for the clutch, don't try to fit one that is not designed for the use as it will stuff the clutch as what happened to bl4ck32's os twin plate when jms fitted/bodged it up to mattr's car.

Bl4ck32, Who was it that sorted out the thrust bearing for your clutch when it went in for balancing with the motor?

[huddy]

thanks cubes

yep i am running standard fork / slave to suit the rb25 box had to change the pivot pall as we originally had the standard one in there and it wasnt long enough and the fork had exess play/movement

the thrustbearing also it could be i guess, but just using the ones that were given when buying the nismo clutch (NOW using the tilton twin plate)

i'm really leaning to stocking the clutch out / and stock thrustbearing / pivot ball just to see if it drives A OK and doesnt slip at least this would then eliminate either problem with 'BOX' or 'CLUTCH'...

and if it is ok with stocker maybe buy a single plate 6 puck new... at least then there'll be no issues with it

-----

BL4ck32 i am interested to hear more about the thrustbearing issue also

thanks

-Matt

[Cubes]

Slip has nothing else to do other than the clutch.

If you have had to play with the pivot its 100% completely obvious using the old thrust bearing setup is 100% not suitable.

Generally when you buy a clutch they come with a thrust bearing.

Every clutch I have bought has.

Grab the suitable thrust bearing that should have came with the clutch, throw in the origional pivot and it will work a.ok.

[huddy]

spoken to a couple more people and have also been told that in some cases you need to get an alternative carrier (from another rb25) as some are longer than others...

person i talked to - had same symptoms as mine - just load it up and it would slip - changed the carrier to a shorter one and it was A OK!...

:S i'm getting a headache...

[Cubes]

Which carrier are you using? The one suited to the rb25 push type box?

[Bl4cK32]

I think they sent my twin plate to Xtreme clutch and they said it had the wrong thrust bearing carrier with it, and thats what may have damaged the clutch (bent metal plates).

I agree with cubes, set it up as per std -std pivot, fork, and slave. Master can stay as rb20 item. Find out the right carrier to go with that clutch for the rb25 box. Then fit the twin and u should be right.

Changing to a shorter carrier may not be the answer. U need to find what length for that clutch in that box.

[Cubes]

Bl4ck32,

I noticed with the new clutch I had fitted the thrust bearing sat noticably forward on the carrier compared to the previous fairly std organic clutch.

I've noted the same with heavy duty clutches in the VS and previous cars.

My guess is, if your OS clutch was bought new to suit an RB25 it would simply come with a thrust bearing, no carier.

That thrust bearing would sit in the correct position on the std carrier in order achieve the correct positioning on the rb25.

Unless its impossible for the given clutch setup to use the std carrier with a specific thrust bearing.

That does sound unlikely as there's nothing special about a carrier that simple modification (when manufacturing) of the thrust bearing couldn't sort out.

Which brings me back to Huddy's problem... Were you given the option to purchase the suitable thrust bearing with your clutch?

It may be possible the clutch has been designed around the std rb25 thrust bearing. I find this unlikely as its easier/cheaper/quicker to make a generic clutch that works in all applications for say an 8" clutch, then use the thrust bearings positioning to achieve the movement required to engage/disengage the clutch.

As you stated you are running the nismo thrust bearing that is smaller and different to standard obviously throwing another spanner in the works.

Get on to Tilton and find out where you can obtain a thurst bearing suitable for an R33 Series 1 RB25DET Push type gearbox.

If they say use the std item.. you beauty.

damn back to my pl/sql home work.

[Syphon]

This will sound really lame but you have been bolting the pressure plate to the flywheel??

heheh

[Cubes]

lol.. Not a silly question..

I've bolted the clutch up but not torqued the bolts up completely only to remember as the motor/gearbox was almost in.

[BHDave]

I've run into similar problems before, the first was when i snapped a diaphram in half on my old os twin plate, which i later found out was due to the stock carrier being longer than the os carrier. I didn't receive the carrier as i got the clutch s/h and didn't know any better. I also ran a stock type thrust bearing.

The second issue is probably more relevant to your question, which was also with the os clutch, was when i swapped master cylinders. I would have had a week wait for an r32 one from nissan, and they had an s14 one in stock so i got that seeing as i had a friend who had used one successfully. The problem was that it didn't have enough travel when installed into the 32 with my setup and so maintained pressure in the system, which when everything got hot (like sitting in traffic) it would just slip like a mofo as the expanding fluid caused the slave to push the fork a bit. I'm pretty certain that it was this situation that actually contributed the most to the failure of the clutch in the end.

The obvious check for that one is to see if you can push the slave cylinder back by hand when the pedal is up. It should move in with very little effort.

I found later that my friends car was also maintaining pressure in the system but as he was only running a single plate there was enough room to move that it didn't start pressing on the fingers.

I am assuming it's something like this as you have already checked for obvious leaks from the rear main seal and the input shaft seal.

Have you over packed the pilot bush with grease maybe and it's spewing out onto the flywheel (doubtful)?

[1400r]

tilton clutch was s/h and had no thrust bearing so just re used the one from the nismo g max a smaller version which I was told was the correct one.

hmmm yippee box out clutch to ACS hopefully they can shed some light

gotta get this fixed soon I wanna see how the 2530 goes on the 2.4lt

[Cubes]

Interesting.. So they 100% do replace the carrier and thrust bearing.

Finally to the bottom of it.