81widemariah

So I need some help guys. I'm an avid poster over at the big board, but I cant access it at work so I figured I'd post here. I just finished my 12a blowthrough build and she's finally driving under her own power after a 9 month hiatus. But, of course, I have a few bugs to iron out. The one that is puzzling me the most is my new clutch slipping. Here's the run down:



RB Race Pressure Plate

ACT Organic (Stage 1?) Disc 225mm

8.5 lb RB Aluminum Flywheel

RB Clutch installation kit ( spacers for installing clutch onto aluminum flywheel )



I am going to post pictures of the transmission as I think that is half of the problem... the trans circled in red is the one that is in the car. The other is the one that I pulled out of the car.











From my research the bellhousing portion of this tranny seems to be S5, but the trans mount location matches that of my 12a, in fact it bolted right in perfectly. So I'm lost as to the year of this tranny. Is it possible to swap tailshafts from S5 to 12a?



When I got the tranny it didn't have a clutch release fork, so I used the one from my 81 tranny. I also swapped over the front trans cover and pivot ball from the 81 trans. I also swapped over the 81 slave cylinder and installed a stainless clutch line.





Everything went together fine with a new throw out bearing and pilot bearing and no weird noises. Clutch uptake is smooth with no chattering and shifts smoothly.



So here comes the issue... the uptake on the clutch is right at the very top of the pedal travel. First gear is pretty fair, shift to second gear and as soon as the turbo builds even one pound of boost the clutch slips and RPM's climb. Classic clutch slipping symptoms.





Here's what I've tried so far. Called RB, they seem to think that the clutch fork is not fully disengaging and that I likely have the wrong slave cylinder installed. So I went and bought a 2nd gen slave cylinder, installed, and bled it last night and it made it worse. I just ordered an S5 clutch fork and should have it tomorrow, but dropping the trans again is the last thing I want to do.



SOOOO... what I'm really looking for here is insight. Are there differences between the clutch forks that would cause this? Could the pivot ball also be a problem? Does anyone agree or disagree that my bellhousing appears to be S5? Any other thoughts as to the cause of the problem?

RicerJ

did you get the right kind of clutch cause there is a bit of a difference between something for a turbo and something for a na from what i have seen looking at clutches for my fc

phinsup

That's a ribbed transmission it's got to be a t2 transmission.



As far as bolting to the 12a, the t2 bellhousing and flywheel are both bigger... As well as the clutch.

phinsup

Actually a miata transmission looks just like that, but requires a different input shaft, otherwise they bolt right up to an 81-84. I believe the t2 tranny has a different starter location then the 1st gen starter locale, but I can't remember if that's correct or not.

81widemariah

the clutch is definitely up for the task it's a proven combination for. 12a turbos.... and definitely not a T2 trans, the look very different and have an easily removable bellhousing. It's an NA transmission for sure. I think it is an S5 bellhousing with a 12a tailshaft. If so then I think I need a clutch fork for an S5.

phinsup

Sorry confused the s5 and the t2 tranny. (that's what I get for reading and typing while i'm driving) and everything else I said was totally wrong because the s5 tranny had the same size flywheel, so disregard that whole train of thought, i was on the wrong the transmission.



Anyhow, back to the topic at hand. I don't see how the clutch can slip unless the throwout bearing is pressing against the clutch. i.e. it's not getting enough pressure to fully engage. It's got to be either the fork, the slave cylinder or the rod between the slave and fork (that one seems like a long shot).