I have read so many bad things about the clutch hydraulic system on the fiero I have been looking into doing something different than just rebuilding my system with stock parts. I bought a new clutch master cylinder, took it apart and thought it looked like it would work ok, it looked like other cmc's I had had apart before, then took my old slave cyl. apart and really did not like the fact of a single umbrella seal, I figured that if I could find a csc piston with two seals it would have to be better, keeping the piston squared in the bore, less chance of air being let, or sucked, into the system etc., thats when I found a 1986 Toyota mr2 csc rebuild kit, that piston has TWO umbrella seals, is the right .812 or 13/16 bore, (are all fiero csc pistons 13/16 ?) and is only $9.00 from any auto parts store, I used the fiero spring, not the the one that came with the mr2 kit, it is way to small. The dimensions of the mr2 piston is almost identical to the fiero piston, so basically its a fiero csc piston with 2 umbrella seals.
I also modified my csc bleed screw by taking some material off of the top and bottom, drilling and tapping the old bleed screw with a M7x1.0 thread, I then got a Dorman speed bleeder pn 12708 that has the M7x1.0 thread, and now when I bleed my clutch I simply push the csc push rod into the slave, the way Archie recommends and can now use both hands to do it, the speed bleeder is a one way valve, it only lets the air/fluid out, a tru one man operation, what really amazed me about this set up is that when I pushed the csc piston all the way in and released the rod, the hydraulic fluid was sucked all the way from the master cylinder, that means all I had to do was "pump" the slave until no more air came out, and I knew when that was because I was standing right there, as opposed to pumping the peddle, which only moves the csc piston less than an inch.
On the www.partsamerica.com web site the have a picture of the 1986 Toyota mr2 csc rebuild kit, if You want to see what that looks like, they also have a pic of the Dorman speed bleeder pn 12708.
I have to tell You that I am really happy with how the speed bleeder works, I cant always rely on someone being there to help me, and it takes both hands to push the csc piston in, and in case You are wondering why I machined the stock bleed screw, I could not find a speed bleeder with the M12x1.0 thread, if anyone knows where to get one, that sure would be easier, I checked Dorman, Earls and Russell's products, I am really amazed that those companies do not make one for the clutch hyd. systems, then bleeding the clutch would be as easy as bleeding the brakes. Thanks

got a + from me. great info!

AWESOME find. That solves the problem for the 13/16 slave (used on the Muncie 4-speed and Isuzu 5-speed). Now someone just needs to locate a 15/16 piston with double seals, so the Getrag folks can have a reliable clutch. I had a CAD file and part number for making a new Getrag slave cyl piston to use a good seal from Parker but I don't know what happened to the CAD file or catalog. Perhaps I will look around for another 15/16" slave.. maybe I'll find something similar to what you did.
Thanks for sharing with us!

EDIT: Here is the pic of the kit:


It's only 10 bucks!

[This message has been edited by Steven Snyder (edited 03-10-2008).]

ttt

This is good info - Thanks!

When I swapped a getrag into an 87 GT automatic I used the 4 speed slave on the getrag.
Works real good as the smaller bore gives more travel to the slave with the same amount
of pedal travel. Fairly easy to adapt.

Bob

nice...
and he only has 9 post so far.

[This message has been edited by buddycraigg (edited 03-11-2008).]

quote Originally posted by OldBob: This is good info - Thanks! When I swapped a getrag into an 87 GT automatic I used the 4 speed slave on the getrag. Works real good as the smaller bore gives more travel to the slave with the same amount of pedal travel. Fairly easy to adapt. Bob

Hey OldBob...You'd better share more good ideas like this with you Fiero buddy in Big Rapids!

-Gary

I am having an issue with my getrag slave as we speak! I wished someone knew of a dbl gasket kit for mine. Great info. though.


RUNDLC

Great post/mod! I to have been having clutch problems. I have used the "Speed Bleeders" on my brakes and made a post awhile back about the possibility of using the speed bleeders on the slave cylinder. One question: You mentioned taking material off the top and bottom, and tapping the screw. I'm confused as to exactly what you reworked. Didn't you actually take material off the top and bottom(?) of the slave cylinder bleed screw hole, then tap the hole in the slave cylinder to fit the new speed bleeder? Please elaborate.

Thanks, Ray in Texas.

Thanks for the GREAT info.

I realized this some time ago with only the single seal on the Fiero piston and was thinking about machining an additional groove for another seal or o-ring to help support the piston (I even made a post about it not too long ago). But that is as far as I went, and now thanks to you, I don't have to think about it anymore.

neat info!

So are we talking getrag or isuzu Master cyl.??? (I take it they are not the same?)

StevenS, YOUR talking like you have been looking into this kind of set up for the getrag Master AND Slave??? What have you found to this point? How can we help??

I want to rebuild my system with something better if available.

quote Originally posted by revin: neat info! So are we talking getrag or isuzu Master cyl.??? (I take it they are not the same?)

The master cylinders are the same for the Getrag, Isuzu, and Muncie 4-speed. They changed the design slightly for the later Fieros (87-88 I think) but they all work well. The master cylinders don't have any issues I'm aware of.

This piston gtu300r found is for the slave cylinder for the Isuzu and Muncie 4-speed, they have a 13/16" bore.

quote StevenS, YOUR talking like you have been looking into this kind of set up for the getrag Master AND Slave??? What have you found to this point? How can we help?? I want to rebuild my system with something better if available.

I've been looking into this for the Getrag slave cylinder. It has a 15/16" bore. However, the only other cars that use a 15/16" that I can find are Mercedes, Porsches, and Volkswagens. The problem with these is... they don't use double seals either! I'm not sure how they get away with it; maybe they have better piston designs, tighter bore clearances, or a different bleeder arrangement.
I found a single seal that is designed to seal in both directions that will fit our bore size, but a custom piston needs to be made. I have a CAD file of the design somewhere.

The easiest solution right now would be to machine an o-ring groove in the existing Getrag slave piston about 5 to 10mm in front of the existing seal, and put a good o-ring on there. This would stabilize the piston and should help seal against positive external pressure.
Any machine shop should be able to do that for you for a small cost.

------------------

1988 Pontiac Fiero 3.4 DOHC V6 5-speed
California Smog Legal!

[This message has been edited by Steven Snyder (edited 03-12-2008).]

quote Originally posted by fffttt1: Great post/mod! I to have been having clutch problems. I have used the "Speed Bleeders" on my brakes and made a post awhile back about the possibility of using the speed bleeders on the slave cylinder. One question: You mentioned taking material off the top and bottom, and tapping the screw. I'm confused as to exactly what you reworked. Didn't you actually take material off the top and bottom(?) of the slave cylinder bleed screw hole, then tap the hole in the slave cylinder to fit the new speed bleeder? Please elaborate. Thanks, Ray in Texas.

I made no modification to the slave cyl. body at all, just took material off of both ends of the bleed screw, drilled and taped the bleed screw, rtv the threads, tightend the modified bleed screw into the slave cylinder body, then put the new m7x1.0 bleed screw into the now modified standard bleed screw, that way I could easily replace the standard type bleed screw in case the idea did not work. Basically, I used the old bleed screw with the correct m12x1.0 thread as a spacer/adapter for the speed bleeder. To bleed the clutch, You open and close the speedbleeder, the modified standard style bleed screw is never touched again in bleeding the system. The reason for all of this machine work is that there is no speedbleeder available with the correct m12x1.0 thread, so I got the smallest threaded speedbleeder I could find that I thought would work, trying to leave more material for the spacer/adapter. Does that help.

quote Originally posted by gtu300r: from what I am understanding from other posts, the muncie/isuzu slave is a better slave anyway, why not just buy one of them new and install the mr2 csc piston?

It has the wrong bore size for the Getrag. The clutch effort will be greatly increased and it will overtravel the pressure plate fingers if the full travel of the pedal is used. The pressure plate fingers can collide with the springs on the clutch hub and cause them to come apart.

quote Originally posted by Steven Snyder: It has the wrong bore size for the Getrag. The clutch effort will be greatly increased and it will overtravel the pressure plate fingers if the full travel of the pedal is used. The pressure plate fingers can collide with the springs on the clutch hub and cause them to come apart.

not according to OldBob and others I have read from on Pennocks, on a previous post (the 12th post before this one) he says he swapped his 15/16" getrag slave to a 13/16" muncie/isuzu slave and it is working fine on the getrag transmission. The difference may be which pressure plate OldBob is using or something like that. Does anyone have a definate answer whether a muncie/isuzu slave can be used on a getrag tranny, or which setup with the muncie/isuzu slave and a getrag tranny CANNOT be used? Where did You get Your information from Steven, do You have more information about why it would not work, or what parts were specifically used in Your situation where the pressure plate came apart? Thanks

OldBob, did You experience increased peddle effort, or hear any strange noises from the clutch, how long have You been using the muncie/isuzu slave with a getrag tranny? Thanks

I'm planning on swapping my Getrag to an Isuzu slave as soon as I can find one. I'm going to address the overtravel possibility by building an adjustable pedal stop so that the travel on the pedal is no more than an inch or so after full disengagement.

Regarding the master, I remember reading way back on the old Fiero Mailing List a post from someone who found that a particular Land Rover model used a slave with a smaller bore that would essentially bolt right up to the Fiero location. That makes sense since Lucas Girling designed and built the Fiero hydraulics as well. The intent of the swap was to reduce pedal travel, which is the primary design weakness of the Fiero clutch aside from the stupid single seal slave piston.

I looked at getting some speed bleeder adapters made for the M12x1 Fiero thread at one point but couldn't find a machinist interested in doing a small run for a reasonable ($10 or less) price. To clarify what modification he's talking about, the stock bleeder screw has a tip designed to seat in the bottom of the hole to hold pressure, so to modify it to accept a speed bleeder the tip needs to be modified to allow fluid to flow when the screw is fully seated. Simply drilling the hole the rest of the way through the screw will accomplish this.

I also looked at the O-ring groove modification on the piston but couldn't find anyone who sold an O-ring suitable for sliding applications and fully compatible with glycol brake fluid. I'd rather go with either a dual-lip seal or a spring-loaded seal, but finding one in the right size and compatible with glycols prooved to be impossible for me.

JazzMan

if piston travel is to great with the non getrag slave cyl used on a getrag then why not just space it back a bit? the bolts seem long enough.

it couldnt cost to much to have a piston machined, mabye cheap enough for one person to buy 20 or so and sell them back to us with double groves, make a kit out of it and it should sell pretty well.

quote Originally posted by gtu300r: not according to OldBob and others I have read from on Pennocks, on a previous post (the 12th post before this one) he says he swapped his 15/16" getrag slave to a 13/16" muncie/isuzu slave and it is working fine on the getrag transmission. The difference may be which pressure plate OldBob is using or something like that. Does anyone have a definate answer whether a muncie/isuzu slave can be used on a getrag tranny, or which setup with the muncie/isuzu slave and a getrag tranny CANNOT be used? Where did You get Your information from Steven, do You have more information about why it would not work, or what parts were specifically used in Your situation where the pressure plate came apart? Thanks

My pressure plate never came apart. I'm talking about other peoples problems. You can see where the pressure plate fingers were pushed into the springs of the clutch disk. This can only be caused by overtravel for one reason or another (wrong slave or excessive pedal stroke due to modifications to the master cylinder pushrod).

I have used the Isuzu slave on the Getrag transmission. I never said it can't be done. You know you can bolt a neutrally balanced flywheel on an 85-87 V6. That doesn't mean its RIGHT.

The Isuzu slave has a 13/16" bore. The Getrag slave has a 15/16" bore. Simple math:
Isuzu slave: 13/16" diameter bore --> 0.518 in^2 piston cross-sectional area.
Getrag slave: 15/16" diameter bore --> 0.690 in^2 piston cross-sectional area.

Ratio between piston area: 1.33. This means for every inch of travel you get from the Getrag slave you get 1.33" from the Isuzu slave. The geometry of the throwout bearing lever is such that you need a maximum of about 7/8" travel with the Getrag slave to disengage the clutch with a stock or aftermarket pressure plate (they're all the same, every one you can get for our cars is just a Luk pressure plate with a paint job). I think the maximum travel with the stock master cylinder gives about 1" with the stock master (anyone know the stroke of the master using the full stock pedal stroke?). This translates to 1.33" travel with the Isuzu slave. That's a significant amount of overtravel.

Someone posted recently on RFT about their experiences with the Isuzu slave on the Getrag and they DID overtravel the pressure plate. They had to shorten the pushrod in the slave cylinder so that the piston would bottom out before the the throwout bearing had travelled too far. Not an elegant solution; now the piston ramming into the c-clip in the slave is what stops the pedal from hitting the floor. A better solution would be to use Rodney's adjustable master cylinder pushrod and shorten it until the pedal doesnt have enough travel from its rest position to the floor to overtravel the clutch. Then you end up with a short pedal throw though.
I used an Isuzu slave with the Getrag for awhile because it was all I had when I did the Getrag swap. I had to be careful to not push the pedal in all the way. The effort was hard but I got used to it. The clutch disengaged with the pedal pushed down only a bit. I am now using the proper slave cylinder and it feels great and there is no danger of pressure plate or clutch disc damage.

quote Originally posted by JazzMan: I also looked at the O-ring groove modification on the piston but couldn't find anyone who sold an O-ring suitable for sliding applications and fully compatible with glycol brake fluid. I'd rather go with either a dual-lip seal or a spring-loaded seal, but finding one in the right size and compatible with glycols prooved to be impossible for me.

I found a double seal that works... but at the moment I don't know where the catalog and notes I took went. I will post them in this thread when I find them.

[This message has been edited by Steven Snyder (edited 03-13-2008).]

Only thing wrong with his idea, is the fact that I did not read it 3 days ago, before I brough a whole new slave, dang! Well at least I did determine when I got the old one off that it was leaking into the boot. That's last time I'll do that. Next time I'm going his route, great idea.

quote Originally posted by Francis T: Only thing wrong with his idea, is the fact that I did not read it 3 days ago, before I brough a whole new slave, dang! Well at least I did determine when I got the old one off that it was leaking into the boot. That's last time I'll do that. Next time I'm going his route, great idea.

You may have needed to replace the slave anyway, if the bore was corroded as often happens. If you have troubles with the new slave you can always put the MR2 piston in it. The new slave just has a single seal.

quote Originally posted by Steven Snyder: You may have needed to replace the slave anyway, if the bore was corroded as often happens. If you have troubles with the new slave you can always put the MR2 piston in it. The new slave just has a single seal.

Steven is right, this is the best time to install the mr2 piston, its only 10 dollars, You will be alot happier for a lot longer with its performance, be sure and put some grease between the boot and the csc piston, on the inside of the slave cyl. bore, put a little in and just run Your finger around it to coat as much as possible, if to much is applied the piston will just push it out of the slave into the rubber boot, the grease will keep water out and maybe keep corrosion from happening as fast and be sure to use the fiero spring, not the little mr2 spring.

What stops someone from using a 4-speed master, or the Wilwood unit, along with a 4-speed slave? That way the master bore could also be changed to adapt the slave bore decrease.

quote Originally posted by gtu300r: Steven is right, this is the best time to install the mr2 piston, its only 10 dollars, You will be alot happier for a lot longer with its performance, be sure and put some grease between the boot and the csc piston, on the inside of the slave cyl. bore, put a little in and just run Your finger around it to coat as much as possible, if to much is applied the piston will just push it out of the slave into the rubber boot, the grease will keep water out and maybe keep corrosion from happening as fast and be sure to use the fiero spring, not the little mr2 spring.

Damn*^&---- moaning sounds..... good point! Thing is, my slave is a bit of a PIA to change on my car, it's under my trubo and custom Y pipe. Yes, it is well heat shielded. I have to get my 87GT project done and ready for Carlislie. Then I will go back and get that piston. I'm also making a whole new setup on my 86 for my intercooler, that + orders to fill......

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[IMG]



Trueleo.com/fiero.htm
RSpiderII@aol.com

Any chance someone could post or direct us to a post with a pic of the stock 4/5 speed piston?

Good find BTW.

Steve

quote Originally posted by Emc209i: What stops someone from using a 4-speed master, or the Wilwood unit, along with a 4-speed slave? That way the master bore could also be changed to adapt the slave bore decrease.

There was a post a couple of years ago about the Wilwood. Can't remember exactly what the downside was other than cost.
search=="Wilwood"/ArchieveTD&Q/entire thread
There are others, but this is the one I remember:
https://www.fiero.nl/forum/A...070315-2-077279.html

[This message has been edited by maryjane (edited 03-13-2008).]

I already know where the posts are about the wilwood. In fact I've already helped with a Wilwood conversion. I'm just wondering about changing the master bore to compensate for overthrow.

quote Originally posted by fierohoho: Any chance someone could post or direct us to a post with a pic of the stock 4/5 speed piston? Good find BTW. Steve

give me a sec, i think i have a pic from where i rebuilt mine...

https://www.fiero.nl/forum/A...070315-2-075401.html

[This message has been edited by buddycraigg (edited 04-01-2008).]

Sorry for the delay in responding to questions. Haven't looked at this thread for a while.

I installed an adjustable banjo on the pedal/master cylinder in addition to the 4spd slave.

I have no indication of "bottoming" of the TO bearing. The pedal pressure seems fine.
I can't compare to previous PP as this was a auto to manual swap.

My wife's 86 GT 4spd is just borderline with enough pedal travel to release the clutch. I added
the adjustable banjo to that one too. I also added a 1 inch block to the top of the pedal to make
it easier to "floor" the clutch pedal.

I definitly will try twin seal piston next time I rebuild a slave.

Bob

[This message has been edited by OldBob (edited 04-01-2008).]

I have an 87GT. I believe it uses the Getrag.

I rebuilt my slave a while back and it crapped out on me again. Although I know the adaptation of the smaller bore would work fine I would like to keep the original slave. Sure wish would could find this type piston for the larger bore.

FWIW- After I rebuilt my slave my clutch worked great. I had no need for additional travel that would be offered by a smaller bore. Seemed perfect. I guess the issue is if anything is wrong with the system and you get the slightest reduction on movement of the slave you run the risk of not having enough travel.

The seal isn't available separately, I looked. I found the original manufacturer a few years ago but their minimum order was like $10,000.

Here's a drawing of the Getrag slave including piston:



JazzMan

Great drawing. Seems the piston is notably shorter than the 13/16" one with double seals. I don't think there is enough room to cut another slot in there.

[This message has been edited by sjmaye (edited 04-03-2008).]

quote Originally posted by sjmaye: Great drawing. Seems the piston is notably shorter than the 13/16" one with double seals. I don't think there is enough room to cut another slot in there.

There is enough room for an o-ring groove for sure.

quote Originally posted by JazzMan: The seal isn't available separately, I looked. I found the original manufacturer a few years ago but their minimum order was like $10,000. Here's a drawing of the Getrag slave including piston:

AWESOME drawing! Thanks for posting that.

I looked around for seals to fit the Getrag bore and did find some. I believe Parker was the manufacturer. They don't fit the stock piston though; they would require a custom piston or some lathe work on the stock piston. I'm still trying to find my notes and the catalog; I have no idea what happened to it! I did all this two years ago so its in the depths of my harddrive somewhere..

does anyone want to send me a getrag piston (I would prefer an aluminum one and slightly used, just to test the theory, wouldnt want to waste a new piston if it was not necessary, besides a half worn umbrella seal would be an excellent start to test the benefits of an o-ring), I have a lathe, and my sister sells o-rings, the reason I mention this is that it DOES matter which material is used, buna, epdm, etc., the o-ring would have to be compatable with the hydraulic fluid, the ones at the hardware store in the plumbing section is not going to work for long, I could machine the piston for someone to test with the o-ring modification, will it work? As for costs, I would have to buy a part off tool to make the groove with, and the o-ring itself, my time etc. The reason I say this is because I was going to do this exact mod on the 13/16 piston until I found the mr2 piston for $9, why would I try?

I am really amazed no one has asked me to make them a speedbleeder for their slave cyl., once You have bled the system this way, any other way is a joke!!!!!! costs, what would it be worth to bleed the clutch by Yourself, anytime You want, hastle free with no special tools or help?

just thought I would offer, any takers?

quote Originally posted by gtu300r: I am really amazed no one has asked me to make them a speedbleeder for their slave cyl., once You have bled the system this way, any other way is a joke!!!!!! costs, what would it be worth to bleed the clutch by Yourself, anytime You want, hastle free with no special tools or help? just thought I would offer, any takers?

Ok send me a PM about the speed bleeder! I'll try it

I found a speed bleeder kit that fits the 5-speed Isuzu slave cylider.

Its from www.racerpartswholesale.com
SB-BMW-S BMW Adapter Kit Silver $15.00

http://www.racerpartswholes.../3854/Speed_Bleeders

BMW Adapter Kit Silver
BMW adapter kit for rear motorcycle caliper. Consists of M7 x M12 bushing to replace the OEM M6 x M12 bushing. Included is SB7100S Speed Bleeder and copper crush washer. Rubber dirt cap.Color silver

The kit is a Speed Bleeder Products, Inc. product marked SBBMWS 7m X 12mm
www.speedbleeder.com