Exedy Twin Disk - can't go into first gear when engine is running!
 

I have 20b mated to FD transmission via Exedy Twin Clutch. I can't get into the first and reverse gears when the engine is running. I can only get into the second, third, fourth, and fifth gears. I can shift into the first & reverse gears when the engine is off. I don't think it's hydraulics because I can slip the clutch in the 2nd gear and get the car moving without issues. I bought FD OEM throw-out bearing new when I bought the twin plate clutch new. Clutch grips fine in boost. Once I'm in the gears, transmission is pretty smooth in all gears. I just can't shift into first and reverse when and only when the engine is running. I'm stumped. Any ideas?

Thanks in advance!

One more thing I should add is when I jack up the rear, clutch is always slightly engaged. I can't seem to completely disengage the clutch. Pedal feels fine. Slave cylinder has been bled properly. Any tips would be much appreciated.

broken clutch fork won't allow clutch to disengage

if clutch fork was broken, I wouldn't be able to shift into 2nd, 3rd, 4th, and 5th gears though, right? I also can get the car moving in 2nd gear... so clutch is semi-working, just not disengaging all the way. I had my shop adjust the pedal link, and still no luck.

pump the clutch a few times and then see if itll go into first. Also, do you still have the stock rubber master->slave hose?

I'll try that as soon as I get home today. I drove it for a few minutes yesterday and symptoms didn't change, but it's worth a shot to try to pump it the best I can. I changed the clutch line to ss braided line.

adjust the clutch pedal ?

put the car into first and then start it with the pedal depressed with the car in an open area.

if the car lurches forward then the clutch needs to be bled, the fork pivot is broken or the pedal needs to be adjusted further.

Pumping didn't work. Adjusting clutch pedal didn't work. We even fab'd longer clutch pushrod which didn't work. Clutch still won't disengage completely. Hydraulics and clutch fork are good (confirmed this by looking at the TO bearing through the access hole. The whole assembly moves in and out approximately 1" as clutch is engaged and disengaged which would suggest that fork is fine). Any help would be appreciated. Thanks all.

I am using RX8 master cylinder... if that makes any difference.

just a thought but seen floater plates stick and won't release one disc completely.


at the 1.41 mark.

just thought i throw this out there. i had similar issue and i noticed my clutch pedal was worn out where the clevis pin goes through.. the pedal was worn out and i ended up taking it to machine shop, they ended up putting a sleeve in it. Fixed the problem!! it had to much play in it before therefore it wasnt disengaging and engaging properly. i hope this helps. Sorry i hope it makes sense what i said english isnt my first language.

It's a new clutch though, professionally installed... I'm leaning towards maybe RX8 master cylinder not displacing enough fluid for the RX7 slave cylinder... This isn't a complicated system, and I feel I went through most if not all obvious culprits. If anyone can chime in on either master cylinders or anything I may be missing, I would really appreciate it!

I'll check that out. I haven't checked where clutch meets at the master.

Clutch pivot is fine... also turns out RX7 and RX8 clutch master cylinders use the same refurbishing kit, so my initial theory is out. Pedal has good pressure. Clutch fork is fine. It just isn't pulling on the TO bearing enough. I'm stumped...

found out master clutch cylinders for RX7 and RX8 both have 5/8" bore. Does anyone know the stroke of RX7 master clutch cylinders? I'm trying to figure out whether RX8 and RX7 masters clutch cylinders are different in stroke. If RX7 has a longer stroke, I can then add larger diameter master clutch cylinder and hopefully be able to disengage the clutch completely. Thanks!

why did you go with the RX8 unit anyways?

it's probably just air in the system, reducing the throw.

It's in an RX8. Pedal pressure is good. No change in pressure after pumping it. solid column of fluid when bleeding it. I'm pretty sure there's no air...

i wouldn't rule out air even after pumping the pedal, it depends where the air is trapped as to whether it will overcome the pressure loss. a solid pedal feel also doesn't necessarily mean there isn't still air in the system.

if it is a matter of clutch throw then you may have to modify the clutch pedal bracket upper stop to give it more throw.

and last but not least, check the clutch pedal bracket for cracks. sometimes it's not apparent but if it is beginning to crack(and they commonly do on the RX8) then the throw will be reduced. the additional tension on the stock RX8 pedal will also crack it sooner(the twin disc is going to require more effort to release, putting more stress on the pedal assembly), so pick up a reinforcement bracket from race roots or BHR. the RX8 clutch pedal assembly is by far the cheesiest thing i have ever seen.


if you want to verify if it is a throw issue or air in the system you can adjust the pedal push rod and lengthen it. don't worry about the pressure applied to the throwout bearing simply for the test but do not drive the car extensively with a preload applied or the throwout bearing will fail prematurely(since it will always be loaded, dragging and spinning which is not ideal but perfectly fine for a short term test).

I really thought it was air too. I had shop owner bleed the whole system which they did and a friend of mine who used to be a mechanic at a performance shop take a look at the clutch, and they both say it's not the air. I did hear about clutch cracking issue. I haven't checked for it specifically. I will do that. Thank you.

It is hard to get all the air out of the salve cylinder when it is mounted.

Loosen the drain valve, remove the slave unit, have the valve in be pointing up, loosen the valve more until fluid comes out. Tighten and reinstall.

I haven't had chance to check out the crack yet, but we did lengthen the rod 0.75" before and that made no difference. I read people complaining about clutch making clicking sound with cracked clutch brace, but mine makes no sound. However, given all the data, it does seem to point to cracked brace... since that would lead to inadequate disengagement despite good hydraulics and lengthened slave rod. If this is the case, I'm driving up to vegas to buy you a lap dance from a bargain priced stripper!

the clutch pedal bracket doesn't take too much to inspect, just dive under the dash with a flashlight and check all the 90* legs that come off the base of the firewall mount. i'm still not sure that is your problem but it is a possibility.

the next possibility would be dragging clutch plates or a cracked first gear syncro. if it is a faulty first gear syncro then a test i would use would be: start the engine and put the transmission into third gear and then reverse, if it goes into reverse just fine and still not first then you likely have a faulty transmission first gear. so the lap dance might have to wait. :)

i also don't know that a professional install would rule out the possibility of a faulty assembly process. the bell ring can't be flipped and all the plates have alignment paint on them but they can be installed upside down. the center disc does have a directional splined gear, if it is reversed it will bind up the clutch.

How did you determine the clutch fork is fine w/o removing it?

The older style clutch forks are known to develop a hairline crack at the pivot. Not obvious when installed. Typically happens when installing a new, stiffer than stock aftermarket clutch.

If the TO bearing is getting pulled enough, that is the exact symptom of a broken clutch fork.

When the clutch fork breaks, it will be difficult to shift into any gear with the engine running - including first and reverse.

I suppose it could be something else too but doesn't sound like it IME.

Thank you for your inputs.

rotaryevolution, I examined every inch of the clutch bracket and nothing gives when I press in the clutch with my hand. Master cylinder is being pressed in linearly as I press the clutch slowly. About the clutch install, I asked the mechanic who installed the clutch and he said he is aware of the directionality and installed it correctly. Given his experience, previously demonstrated honesty, and attention to detail, I trust him.

By the way, when I jack up the rear of the car and turn on the engine with clutch fully depressed, the rear wheels still turn in all gears. This is the reason why I don't think tranny is the main culprit. It certainly can be, but foremost culprit is still some component of the assembly that operates the clutch or clutch itself.

I think the easiest thing to do would be to blame potentially shorter throw of the RX8 master clutch cylinder compared to the RX7 master clutch cylinder (if anyone knows they're exactly the same, please let me know). Both master cylinders are the same bore, and in fact uses the same refurbishing kit, but perhaps shorter throw by RX8 master clutch cylinder doesn't displace FD RX7 slave cylinder enough. To fix this potential problem, I plan on changing the RX8 master clutch cylinder with a larger diameter Wilwood model to transfer enough volume to RX7 slave. I'm going this route mainly because this is the only route that doesn't necessitate dropping the tranny again. If this doesn't work, I'll drop the tranny and look at the clutch & fork more closely.

Any suggestions would be really appreciated in the meanwhile!

Well another cause of trouble shifting into gear when car is stopped with engine running can be pilot brg issues... but you would probably also notice a rumble or noise while clutch is depressed?