Drama After Rb25 Box Conversion

[FATGTS-R]

Ok Just picked the car up tonight after it had an RB25 box bolted to the back of an RB20.

The clutch is a twin plate and previously with the rb20 box it had a VERY heavy pedal and was very on/off in operation as you would expect of a twin plate.

With the RB25 box I also purchased a new slave cylinder from Nissan.

During the conversion the mechanic rang me and said the clutch seems to be fine and no need for a new one.

He then called me today after the road test and said the clutch was dead as it was slipping profusely. I thought this strange as it never even thought about slipping prior to the conversion.

Anyhow, I picked up the car and instantly I knew something was amiss. The pedal was no longer heavy to push, in fact it is lighter than my daily RB30e oz skyline. It also was no longer "on/off" in operation, it was easy to use, although it was nice I knew it wasnt right.

The other najor issue is the amount of free play before you feel any pressure under the pedal. Basically from its fully disengaged position to fully engaged(firewall) 85% of the travel is free play with the last inch or two getting some resistance.

I mentioned that to him and he said its probably because of the R33 "possibly" having a larger slave cylinder.

I asked if it just needed some adjustment and he said no? Mentioning something about the fork and that there was no other adjusting to do or something along those lines.

I didnt understand, hence I have come here for some advice. If I need a new clutch then so be it but I am puzzled as to how it was holding 285rwkw without batting an eyelid and then with the new box slipping like crazy? And why the insane amount of freeplay that he says cant be changed?

Apoligies for the long post but just wanted to include as much information as possible.

Any help would be much appreciated.

Thanks in advance

Jayson.......

[Bl4cK32]

take it somewhere else.

Under the dash where the clutch pedal is there is adjustment for the pedal.

I assume he changed the thrust bearing and carrier over as well? The thrust bearing and carrier need to be the right ones for the clutch / box u are using otherwise u end up killing the clutch. The morons who fitted mine didnt use the right carrier and it warped the metal plates in the os twin 40 thou.

Probably just needs adjustment...

[FATGTS-R]

Hmm interesting. He told me the old thrust bearing was cactus and he replaced it.

Would using the wrong thrust bearing/carrier give the same situation I am experiencing with the long pedal?

Also with the pedal adjustment, isnt that for the "pedal" free play? i.e there is a few mm of pedal play, and then a mile of "different" free play, if that made any sense at all? A mate said pedal free play, and slave free play are different and that mine has a mile of slave cylinder free play but he has nfi how to adjust that.

[Bl4cK32]

your best bet is to go to a gearbox workshop. They can tell u straight away whats wrong etc...

With the box in the car the clutch fork should sit up against the slave pin.

Wrong size carrier would mean the clutch isnt fully engaged when changing gears. If he reused the rb20 carrier and just changed the bearing, id get it looked at.

Have u tried adjusting the pedal adjustment under the dash? Is the clutch bled properly?

There is too many variables to diagnose over a computer...like was all the rb25 parts used -fork, slave etc...

Edited October 27, 2006 by Bl4cK32

[FATGTS-R]

Thanks for the replies mate and yes I have full intention of taking it to a specialist to get it looked at.

Just put it up on here incase it was something simple I could fix myself.

I'll give the pedal adjustment a go in the morning.

[R31Nismoid]

Should have taken it to Racepace

Might cost you a little more, but you'll never have an issue

[Wheezy]

Should have taken it to Racepace

Might cost you a little more, but you'll never have an issue

Reacharounds for all j/k

Sorry to hear about the conversion still not going smoothly Jayson. Youll get there mate.

[legend01]

I've done this same conversion with no issues the rb25box bolted up with no adjustments necessary used the same clutch and bearing just changed the slave cylinder as you have done and all was fine only differance that i can see was the twin plate clutch I used a single so I'd say the've done something wrong there somewhere

cheers Peter

[T04GTR]

you need to back off the clutch slave. its pumping up. i garentee it. he probably couldnt beed it properly and just adjusted the master cylinder push rob to compensate. butnow its not releasing pressure and its pumping up. back it off so theres good flop in the pedal or your clutch will die very quickly

[legend01]

found this intresting might help you http://www.skylinesaustralia.com/forums/in...howtopic=117570

[FATGTS-R]

TO4GTR, thanks for the advice. There is plenty of flop in the pedal.

legend01, thanks a million for the link. The poster has the identical problem to me as did someone else and I dont think it was a coincidence we all had OS twins. Unfortunately he didnt get to the bottom of the issue and installed a new clutch.

From reading through it though it seems highly likely its a bearing/carrier issue. So looks like the box is coming off again.

Thanks for all the help guys. I'd love to say I will report back when I find the issue but I dare say if the box is coming off again I will just reove the twin,sell it, and have a chat to Jim from QLD.

[T04GTR]

ar yes. the old to thick carier issure. i should point out there needs to be flop in the clutch fork to

if its a twin you need a 12mm-14mm spacer

the bearing is a datsun 1600 item. (small diameter running surface)

[FATGTS-R]

Ok well I had a discussion with the workshop this arvo and they are adamant its not an installation issue and its the clutch.

He told me he measured everything up before installation and he used the correct sized bearing. Also said he needed to use a different carrier and also used a shorter pin in the slave to accomodate for the twin plate.

Lastly, he said "get under the car and try and push the fork towards the slave, if there is freeplay there then that means the clutch is fully engaging and disengaging and its a clutch problem"

So under the car I go, and yes, I can push the fork towards the slave about 5mm before the fork hits the housing.

I then rang my usual mech (who I didnt go to as he was booked out and I needed it back urgently) and he said that it seems that its 90% likely that infact my clutch is gone based on being able to push the fork back towards the slave and he might infact of used the correct bearing/carrier. When I mentioned the pedal issue, he said (as TO4GTR did) that its just an adjustment under the dash, but will have no effect on the slipping issue.

From the above information, does it sound likely that the workshop infact did the right thing and that I need a new clutch?

As mentioned, the clutch was fine before. But when the old box failed it got jammed into fourth gear and I had to ride it in fourth to get it going to limp it home for 50 metres. I only road the clutch for about 3-4 seconds, about 5 metres, to get momentum.