still having clutch problems...

[rb250sx]

Ok, i put the transmission back up for the third time today, after trying everything you guys have been saying to try except replacing the pilot bushing, it still wont go into gear when running. So now im going to drop it yet again and replace the pilot bushing. But before i do i want to make sure there is nothing else it could possibly be, here is a list of what i have done and some things i would like to rule out.

What I have done:

flipped clutch disk around (is currently in correct)bled the system several times (positive there is no more air in the system)adjusted the pedal (fork is moveing all the way, and adjusted to see if it was going too far as well)

Can i rule out?-clutch disk and pressure plate. I got these from JDM Parts Plus, they didnt give me the correct disk at first because they screwed up the order, but it was still a disk for a 300Z, just a little harsher, so i kept it because i didnt want to wait any longer. It is a 4 puck sprung ceramic clutch and i compared it to the old clutch, same diameter spline fits fine, the only difference that i was wondering would make a difference is on the old clutch there is a piece thats sticks out about a quarter inch on the flat side of the disk where the input shaft goes rather than being completely smooth. I dont think this would make a difference but let me know if you think it would otherwise. -Driveshaft. Sounds dumb, but could the yoke be going in too far causeing problems? it sits about an inch to an inch and a half out from the rear of the transmission, so it sits where it should be but i just want to rule this out.

I really cant think of anything else, i didnt think it was the pilot bushing before because it was the bushing that came with the engine, and it was a manual to begin with. It didnt look mushroomed and it sits about an 8th of an inch inside the lip of the flywheel.

If there is anything else anyone can think of please let me know, ive had this transmission down way too many times and im getting frustrated haha.

[Andrew85cm]

Sorry you are having so much trouble. I know it sucks when you do all this work to have something like that not work. My motor came with an auto transmission. I also got a manual transmission but I had no flywheel or anything so I had to source one out (THanks Cameron). Anyway I had to pull my motor 3 times because of my mounting choice I was not able to get the transmission out without the engine being removed.

My problem was with the pilot bearing inside the actual engine. I guess this is what you are talking about switching out. It is vital when replacing the clutch to replace this cause they wear out along with the clutch. I did not replace mine and my clutch would make the weirdest screaming noise when it was engauged. It did however run like that. My problem was the bearing is totally different in the auto than the manual bearing. I replaced it and it ran fine. I don't know your situation but maybe replacing it is the key. I assume you also replaced the thrust bearing. Also do you have a 300zx NA clutch because the TT clutch is entirely different. I don't know if any of this helped but good luck.~ANDREW~

[rb250sx]

Thanks for the reply. yah i know the auto bushing causes a problem goofynick had problems with his, but mine was a manual to begin with. Just curious, im not sure which clutch Justin and Glen ordered me whether an NA or TT, what exactally is the difference between them?

[Andrew85cm]

The difference...I don't know but one thing I do know is that the TT clutch won't work so it must be different enough. That is worth finding out before you put it back.~ANDREW~

[rb250sx]

Well, i posted on some Z boards to find out the difference. Once i drop the transmission back down again ill take a micrometer to the new disk and my old disk and see how the thickness varies. I would throw the old disk back in just to see if it works, but it got rusted up pretty good from the fire and i dont want to throw it back in there. If anyone else has any ideas please let me know before i drop the transmission again:-) thanks andrew

ALSO: if anyone has any contact information for justin or glenn at JDM Parts Plus aka UP-Speed garage please let me know. I know justin moved away, and all the numbers were shut off. But im sure glenn is still around somewhere. Scott Buwulda(sorry for the spelling) was in pretty close contact with them i think, If you are still around scott please help me out. thanks

[Imissmyturbo]

There was a car that a friend of mine has that had the same problem. It was a KA motor. He could not put the car in gear while it was running. He tried bleeding the system and replacing both the master and slave cly. If you would put the car up on the lift it would go into gear because the rear wheels could spin. I am willing the bet if you would push your car you could get it into gear with it running. The problem was his piliot bearing wasn't in strait and it woudln't let the input shaft for the transmission come to a stop. So based on what you are saying I bet there is a problem with the piloit bearing.

[rb250sx]

Thanks everyone for your help. It seems that the difference between the NA and TT disks is bout 4mm in diameter. This doesnt seem to be the case with my disk, though i will double check when i pull the transmission back down. I guess the thinkness of the disks are the same, so this shouldnt cause a problem, which leads me to believe its more the pilot bushing. Im going to jack the rear end off my ramps and try to put it in gear, but it going into gear with it up could be any situation which didnt stop the input shaft from spinning correct? anyway, ill let you know how it goes this weekend when i drop it back down. thanks again.

[GochiraR32]

It is a 4 puck sprung ceramic clutch and i compared it to the old clutch, same diameter spline fits fine, the only difference that i was wondering would make a difference is on the old clutch there is a piece thats sticks out about a quarter inch on the flat side of the disk where the input shaft goes rather than being completely smooth. I dont think this would make a difference but let me know if you think it would otherwise.

I have experience something like this on another car. If you are talking about the clutch plate center piece and it is 1/4 off in depth, then the your clutch might be constantly engaged. While your car is off you can run through your gears, while it on you cannot. Another thing it might be is the hydralic connection attached to the transmission. If it is not on tightly or missing a bolt, then when you step on the clutch it will not disengage.

Hope this helps.

[rb250sx]

Here a picture of what im talking about. its the only pic i have right now until i take the transmission back down, but hope it helps.this is the side of the disk that touches the flywheel. The very center is flush with the rest of the disk, whereas on the stock clutch, it actually raises up about a quarter of an inch. is that what you are talking about gochira?

[GochiraR32]

I was thinking you put the clutch backward by mistake, but as you described it is install correctly. Do you know if the T/O bearing is making contact to the diaphram? If not, the clutch will not disengage.

Also are all the RB25 clutch setup the same? Meaning they are all push type, and not pull type like the later BNRs?

[rb250sx]

All 25 clutches are push type as far as i know. And the TOB must be making conatact because there is a lot of force on the fork. I will know more once i get the transmission back down this weekend, but you have helped out a lot. I appreciate it.

[BoostFab]

i would certainly double check the pilot bushing, as some mentioned above.

[rb250sx]

well, i changed the pilot bushing this weekend and still no luck. i measured evey part and compared it to the old ones, and the clutch disks dimensions are the same except its a little bit thinner. but what i did notice is on the new pressure plate, the plate sits a 1/4" closer to the flywheel than the old one. I didnt know if this was just because of use the old one may sit back more, but i think this could possibly be my problem. The other thing i thought of was that i never put a step in my flywheel, however i know people who didnt step their flywheels and never had problems. I guess im going to try to replace the pressure plate now, does anyone recomend a decent one? or should i just get a stock replacement? The one i had was made by Competition Clutch, but was given to me by the guys at JDM parts plus, so im not exactally sure what it was for, but it bolted up fine. Also, i was thinking if there was a slave cylinder taht woudl push the fork back farther and possibly release the pressure plate more. Thanks.

[Andrew85cm]

Some RB25s did come with pull type transmissions for a short time. I actually saw one in person at a place in Charlotte, NC. You are gonna have serious issues if this is your problem but I am sure you could tell which it is.~ANDREW~

[goofynick6]

Sounds like it is time for a clutch that other people know works for sure...that sucks man. You'll get it though, just keep at it.

Nick

[rb250sx]

well, i emailed Competition Clutch to see if there were problems with their pressure plates or disks before and what part numbers i could find on the pressure plate to find more information about it. so i will see what i get back from them.

btw, what is your opinion on finding a longer slave cylinder, does this seem like a logial fix?
Modified by rb250sx at 3:48 PM 4/18/2005

[rb250sx]

well, i got an email back and apparently my pressure plate was an older design that they were having some problems with being set wrong. He is checking on some things for me, but hopefully all will be fixed:-) I wish i knew all this before the transmission was down 4 times haha

[GochiraR32]

but what i did notice is on the new pressure plate, the plate sits a 1/4" closer to the flywheel than the old one. Also, i was thinking if there was a slave cylinder taht woudl push the fork back farther and possibly release the pressure plate more. Thanks.

1/4" might not look like much, but if it is not pushing the diaphram far enough then it won't disengage. Also I hear lot of people had problems with their slave cylinder getting stuck or sticky. Did you have someone step on the clutch while you inspect the slave cylinder for movement? Try putting on an OEM/like OEM 300zx NA plate (it's really cheap), and see if that will work. If it does, then the problem is your aftermarket plate.

I think you are close to solving your problem, and you will get to drive your beast soon.

[rb250sx]

Well, I talked with Chris at competition clutch today, and he took care of everything. what happened is my plate was a prototype that was never released to market, and the offset was wrong. He thought he got them all back, but apparently there was still one out there(mine) haha. He actually worked with Glenn at JDM Parts Plus a long time ago, and thats prob how the plate got to me. So a new plate is on its way and the car should go into gear now:) Thanks for all your help guys!

[red240zenki]

Also are all the RB25 clutch setup the same? Meaning they are all push type, and not pull type like the later BNRs?

Yea, the R34 RB25DET is pull type. I know, because I have one.

[goofynick6]

Woohoo, awesome new Fritz..finally an answer!