OK for ever and ever people have complained about the Fiero Clutch Hydraulics. Originally from the Factory, There were 3 different bores available in the slave cylinder.
The smallest was the Isuzu Slave Next up was the Muncie Slave, which externally was almost identical to the Isuzu slave. Then there was the Getrag Slave, which is shorter, fatter and does not use studs on the slave to mount it.
It became common practice if anyone had a 4spd Muncie they would swap on the Isuzu slave and the car would shift like butter. For whatever reason the aftermarket agreed with this swap and started using the SC37795 slave for all Isuzu and Muncie applications. Now the Getrag however used a different mounting style, different bore and different length push rod and a physically shorter slave.
I had heard of people modding the SC 37795 Isuzu slave for use on the Getrag, but after reading several threads on here, I couldn't find a single one that explained step by step how to do this. Even any rough info that I would need. So I decided to document my conversion and post up all the info I can get my hands on.
Now the prices were a wild difference.
The Isuzu 5spd / Muncie 4spd was $39 at the local Napa The Getrag 5spd was $140 at the local Napa.
My 88GT had a small hydraulic leak in the clutch, I would loose about 2 ounces of fluid after a week of driving the car. I knew it was coming from the slave as I had peeled back the boot and found the lost fluid. This went on for months, until one day it finally gave out. I filled up the master, drove the car around the block, before I made to the store, the master was empty. About 5 clutch pushes would empty the master.
So I popped down to the local Nape and grabbed an SC37795 slave. I pulled the Getrag slave off the car, and brought it into the garage to study the 2 of them.
1st note. Isuzu slave is longer. 2nd note Getrag slave, does not use studs in the slave. 3rd note. Getrag slave rod is shorter. 4th note. On the Getrag slave the bleeder screw and Hyd line are exactly 180 degrees apart. However the Isuzu is about 160 degrees apart. It proved not to be an issue as when mounted the bleeder screw is still at the top, its just the Hyd line that sits about 20 degrees of to one side.
You can see the physical size differences in the lower pics.
The Holes in Getrag slave are 11/32's So remove the studs from the Isuzu slave and drill the holes out to 11/32's Drilling the cast slave is a bit of a pain, but can be done. With a simple hand drill.
Next up, note the different slave rod. You have to use the shorter Getrag slave rod.
OK so now you have a small bore slave, that is drilled out to accept the studs on the Getrag case, and you have the shorter Getrag slave rod.
Just install, bleed the system and test it out.
The first few times I pushed it in, I went really slow and listened for any sign of binding due to the extra throw. The pedal is about 50% harder to push in as well. I did not hear any issues, so I fired up the car, pressed the pedal in, and ran through the gears. Smooth as smooth could be. I took the car for a drive, and tested release/engagement points. To shift now, you only have to go half way down from a dead stop, and if you are like me and rev match all your shifts (when done correctly you can actually shift without using the clutch at all) I only go down maybe a 1/4 of the way and it clicks through each gear perfectly.
It will take a while to get used to the much firmer pedal. I am sure once my leg gets use to it, I won't even notice the difference. The slave went on without any issues, bleed out perfectly and car drives wonderfully. Being as this slave is 1/4 the cost of the original Getrag slave, I wont ever even worry about a rebuild kit. If it starts to leak, I'll just toss it out and get a new one.
Overall, I fixed my cars shifting issue, saved myself $100 and it took me longer to write this post then it did for me to modify and install the new slave. Not a bad days work.
------------------ 85GT,93 Eldorado 4.9, 5spd Dual O2 Custom Chip, Custom Exhaust. MSD Everything Capt Fiero --- My Over View Cadero Pics Yellow 88GT 5spd Full Poly Suspension, Lowered 1/2" in front, Corner Carver.
[This message has been edited by Capt Fiero (edited 12-01-2008).]
This slave, the isuzu one, is that for 5 speed trannys? cause i was having a ***** of a time finding it anywhere else, but napa, for 31 something and some tax. and i was skeptical it was the right one, cause it was so cheap compared to the wrong ones i paid 70+ dollars for at advance. i am fairly sure i cant reuse my old slave and i'm hoping this one that comes in tomorrow is correct.
Those cast iron slaves are usually crap and die quickly due to porosity in the castings. The GM slave cylinder, at least for the 282, is a fabbed steel unit.
As for the Cast verses the Steel. I would use a steel one if I could find one locally. However even if I go to a Delco dealer, they supply me with the cast one, and put it in a Delco box.
One of the things I was thinking was using an old dead Getrag slave, putting a stainless pipe inside of it, then using the MR2 Double check valve slave piston inside the stainless insert. Would take some tweaking to make it right, but I am sure it could be done. However for the time being. I am happy with what I got.
------------------ 85GT,93 Eldorado 4.9, 5spd Dual O2 Custom Chip, Custom Exhaust. MSD Everything Capt Fiero --- My Over View Cadero Pics Yellow 88GT 5spd Full Poly Suspension, Lowered 1/2" in front, Corner Carver.
If you take the part number and go to Amazon.com you can frequently save money since Amazon generally has free shipping on orders over $25.
I, too, have been thinking about using a sleeve to reduce the Getrag bore to 13/16", that's the MR2 slave bore. It will take some precision machining I think, as I have yet to find any DOM tubing in that size range.
As for the Cast verses the Steel. I would use a steel one if I could find one locally. However even if I go to a Delco dealer, they supply me with the cast one, and put it in a Delco box.
The steel ones are as rare as hen's teeth these days. A chrome plated one on a show car would really look good, though.
I'm doing some work looking at having better quality slaves made. Time will tell. They will have double seals if I can get them made in better quality than what is out there. Should be one item the FS can't copy.
------------------ Rodney Dickman
Fiero Parts And Acc's Web Page: www.rodneydickman.com Rodney Dickman's Fiero accessories 7604 Treeview Drive Caledonia, WI 53108 Phone/Fax (262) 835-9575
If somebody can get me the dimensions we need I may be able to help out. I work at a machine shop and if I came in on a weekend and a machine was free I could most likely make something up for you guys. I would make 1 for somebody to try and if it works I would make a run of them. But I need dimensions first and then a trial run. I have a muncie right now and I need my car for a DD so I cant take it apart.
Give me a little while. I will need to convert everything to SAE measurements. Nobody I know has metric equipment or measuring tools to double check the work the machine will do.
Reduce the diameter to 13/16" to use the MR2 piston assembly:
JazzMan
You'll have to make it a little longer, to compensate for the reduced diameter. The piston will travel farther with a given master piston movement. And the drawing is of a steel slave, so only the inside dimensions are (for the most part) important.
You'll have to make it a little longer, to compensate for the reduced diameter. The piston will travel farther with a given master piston movement. And the drawing is of a steel slave, so only the inside dimensions are (for the most part) important.
The length will not change. The disengagement throw of the clutch will not change. The difference in throw will show up as reduced MC (and thus pedal) travel required to disengage.
Get a Length of stainless pipe, Must be 15/16" OD 13/16" ID which would be a wall thickness of 1/16" which is actually a fairly common size.
You'll need to cut 2 1/4 inch slits in the end of the pipe to allow for fluid to access the bleeder screw and come in from the feed tube. Then you are going to need some sort of sealing agent on the outside wall of the pipe so when you press it inside the bore of the Getrag slave there won't be any chance for leaks between the new sleeve and the original bore. Then add in your MR2 piston, and replace the original C-Clip on the end.
I was actually thinking of using JB weld as it is really tough stuff and I don't think break fluid will dissolve it. Especially considering the really really thin area it has to stop fluid from sneaking by.
Seeing as the master does not blow the piston out the end on a 13/16s bore slave right now, I don't think that will even be an issue with your new system. I have access to stainless pipe, and I have a diagram in my head on how this will work. I am no good with cad, so I really can't post it on here. Unless someone has some Betazoid ESP thing going on.
------------------ 85GT,93 Eldorado 4.9, 5spd Dual O2 Custom Chip, Custom Exhaust. MSD Everything Capt Fiero --- My Over View Cadero Pics Yellow 88GT 5spd Full Poly Suspension, Lowered 1/2" in front, Corner Carver.
Well I have had it on there for nearly a week. I spent the last 2 days out with my Wife, doing Christmas shopping, spending hours at a time driving from mall to mall, tons of traffic and I think this has been the best mod I have done to the car in terms of drivability.
One thing I have noticed and its all due to the smaller bore, the point on the pedal between engagement and full engagement is very short. The clutch comes on MUCH faster. It took me a few days to get use to the fact that you don't really slip it out, you rev it and engage it very quickly. Its a nice feeling once you get used to it.
Another note, I thought my clutch was on the way out, I was getting horrid clutch chatter at times, the chatter is completely gone now. My only guess is that it was the old slave and the piston must have been dragging and causing the clutch to engage oddly.
All in all I am very happy with the results.
------------------ 85GT,93 Eldorado 4.9, 5spd Dual O2 Custom Chip, Custom Exhaust. MSD Everything Capt Fiero --- My Over View Cadero Pics Yellow 88GT 5spd Full Poly Suspension, Lowered 1/2" in front, Corner Carver.
[This message has been edited by Capt Fiero (edited 12-07-2008).]
Well just a quick update. I guess I should have expected it, when you have 2 used parts and you put on 1 new part that relies on the first part, the used part is going to fail.
It was what a week and a half ago, that I did the swap, I usually keep an eye on the master level whenever I open the front hood to grab something. Yesterday I noticed it was a bit low. I just chalked it up to air working its way out. I topped it up and drove it. Then this morning I drove the car again.
This afternoon I was looking for my spare backup coil and had to go into the front compartment, the res was damn near empty. First thing I checked was the boot at the slave to see if I had gotten a bunk slave. Nope dry as a bone. I reached under the dash and followed the rod for the master to the boot and instantly knew what was wrong. It was soaked with brake fluid. The master has let go. Fortunately I have a few spares here that I can swap on. Then rebuild this one and put it back on the car.
So just a heads up. If you do the slave mod, you may end up with a bad master at some point.
------------------ 85GT,93 Eldorado 4.9, 5spd Dual O2 Custom Chip, Custom Exhaust. MSD Everything Capt Fiero --- My Over View Cadero Pics Yellow 88GT 5spd Full Poly Suspension, Lowered 1/2" in front, Corner Carver.
So are you saying that the mod you did adds more pressure causing the failure? Or did you just have an old master and as time shows they fail after a while.and it was just time to fix the master?
You need a different pushrod to center everything in the bore like it was, or you may be hitting the end of the slave and it will break it soon enough. Quoted from my post on this
This is for you all that don't get enough throw to get the clutch to disengage. After you have tried everything else. Sorry no pics. For V6 5 Speeds.
Get a 4cyl 5sp slave. It has two studs in it, knock them out and it will bolt right up. The pushrod is a different length, so use the pushrod from the V6 slave BUT put in two nuts that are 1/4 inch wide so you get another 1/2 inch, in the slave hole, then the pushrod against the nuts. This will make the slave sit back just as far the the V6 one but will give more throw, as the 4cyl one is a smaller diameter bore. See below. ..................| XXXXXXXXXX|x XXXXXXXXXX|x XX--------- XXXXXXXXXX|x ^ ........ ^ ....SLAVE......|. NUTS...PUSHROD
The 4cyl slave is even cheaper too.
I tried EVERYTHING lots of different V6 masters and slaves, bleed it 50 billion times, 50 billion diferent ways. Perfectly straight steel clutch pedal, bushings not worn, etc. This works so great, I'll never go back.
I was thinking about that, and if I have an issue, I'll take the longer rod, cut it down so its about an inch longer than the getrag slave rod, and use that. However since I installed the new master everything seems good. The aftermarket master I had in stock was a cast unit as well.
------------------ 85GT,93 Eldorado 4.9, 5spd Dual O2 Custom Chip, Custom Exhaust. MSD Everything Capt Fiero --- My Over View Cadero Pics Yellow 88GT 5spd Full Poly Suspension, Lowered 1/2" in front, Corner Carver.
I meant to update this thread a week or so ago, I have been driving on this for over 2 months using it as my daily driver in City traffic, so you know the clutch gets a hell of a work out. After replacing the master shortly after the install, everything has been perfect. Not sure if my leg just got used to it, or the pressure plate got used to being moved that extra 1/2 inch at the bottom, but in either case, the car shifts very well, pedal feel is awesome and I have not had to add any clutch fluid to it at all in over a month. So all in all I am really happy.
Just don't forget to install the Isuzu spring cause the MR2 is too short and weak . Don't know if it had been mentioned in this thread , just in case And Capt Fiero you did a very useful thread . Got mine working for a month now , never had such a good clutch pedal since i own the car .
The aluminum slaves I am making for the Getrag will be the same bore size as the OEM GM Getrag slaves. 23.86 mm. They can make them a smaller ID but not as small as the Isuzu slaves. 22.1 mm. The Isuzu slave is about 20.85-20.90. I am hesitant to make them smaller. GM made them this diameter. I have an OEM GM Getrag slave in my 88 and it works great. My pedal is near perfect in my opinion. I wonder what my tooling fee might be if I made a smaller slave for the Getrags in the 22.1 mm bore diameter and offered it as an optional slave for the Getrags.
------------------ Rodney Dickman
Fiero Parts And Acc's Web Page: www.rodneydickman.com Rodney Dickman's Fiero accessories 7604 Treeview Drive Caledonia, WI 53108 Phone/Fax (262) 835-9575
Can you hard-anodize the inner bore surface on these aluminum slaves? That'll reduce wear from dirt and grit that will get trapped against the piston seal due to the bore surface being exposed to air all the time except when the clutch pedal is pressed.
My dream cylinder would have a stainless cylinder liner.
Just another update I did this mod several months ago, FieroChick and I just got back from a 3000km road trip and I did not go through even one drop of clutch fluid. Everything worked perfect. I'll be doing this mod to our other 2 getrag cars this summer. Both our V8 Fiero's are now running Getrag 5spds, so at least one part will be cheap to replace on them.
------------------ 85GT Soon to be 87GT,93 Eldorado 4.9, 5spd Dual O2 Custom Chip, Custom Exhaust. MSD Everything Capt Fiero --- My Over View Cadero Pics Yellow 88GT 5spd Full Poly Suspension, Lowered 1/2" in front, Corner Carver.
Its not specifically for the 86GT its for any 4spd car. 85GT, 85 2M6, 86SE and 86GT.
Great! I just checked with my local autoparts supplier using your part number and they have one in stock. So I will pick one up this week and give it a shot.
Which bleeding technique did you happen to use after you replaced yours?
i have adopted your suggestion of using the isuzu slave for the 5 speed getrag. my situation is somewhat ususual in that is have swapped a 4.3l v6 using archies adapter and a centerforce clutch. all was well until i began having trouble with getting itnot first gear then into others. with the centerforce clutch and pressures plate i needed 1" of slave travel to completely disengage the clutch. could not get the travel with the getrag slave. went to the isuzu and a longer bolt and eventually got the 1" travel. many thanks for your info. bled the getrag by the archie method and still am getting small bubbles out.
imo, the entire design defies any logic. fluid source flowing downward, then horizontal, then upward. the pressure differntial from high to low is negligible. this is not like brake lines where all flow is downward. the fiero slave is more like a siphon flow. the factory pressure injector is most reliable fluid moving under positive pressure, not subject to the leakge of vacuum or lack of pressure of gravity flow.
hter is so much misinfo out there it is sad. the centerforce people said 1/2" of movement of the pressure plate will release the clutch. nonsense. maybe some other design , not here. i measured to clutch external arm throw needed to release my clutch. it is 1" minimum. some may take exception, but with the 5speed getrag this is fact.
thanks to members like yourself these cars will survive. i used this chassis to build a lamborghini diablo so my investment in time and money was substantial.
Been running this for roughly 8 months and put it through a ton of speed shifting, so really smacking the pedal down quick and damn near side stepping the clutch.
Stuck in Traffic that got the engine bay so hot, you could actually see the heat waves coming out the rear deck.
Accidentally ran the car so lean that the exhaust from the Manifolds down to the base of the Y-Pipe were cherry red Effectively baking the slave. I did note the clutch pedal did feel "different" however still functioned perfect.
My left leg is totally accustomed to the heavier pedal and feels weird jumping into a normal clutch Fiero. I am going to be doing this same mod to my V8 Fiero with a Getrag in it.
This has been the best 39 upgrade I have ever done to a Fiero.
My only concern now is after all this abuse, I can sorta feel the clutch is starting to go. (I've put 50,000kms on this car, and never replaced the clutch, so I have no ideas how many miles were on the clutch when I got it.)
------------------ 85GT Soon to be 87GT,93 Eldorado 4.9, 5spd Dual O2 Custom Chip, Custom Exhaust. MSD Everything Capt Fiero --- My Over View Cadero Pics Yellow 88GT 5spd Full Poly Suspension, Lowered 1/2" in front, Corner Carver.
So what was the final length of the pushrod you ended up using? I know you used the getrag one but did you end up lengthing it any. I have some steel rod the right diameter that I just need to cut down. Any idea on the length? Anyone know the stock getrag pushrod length?
I just scored a getrag and everything needed to install. The only thing that's missing is the slave. I'm not sure which, but I have 2 sitting around that are either isuzu or muncie slaves would like to modify one to work. I'm not sure which cause I've run both of those trans at different points in this car and just don't remember which is actually on there. I have a cast one on the car but I also have an OEM steel slave sitting on the shelf that would be an excellant choice. It just needs a rebuild. Any help on the rad length would be greatly appreciated.
EDIT: Congrats David on becoming a new daddy!!! Wishing all the best to you a Lisa and of course a big welcome to little Arianna Cassandra Bergquist!!!
[This message has been edited by Fieroseverywhere (edited 11-04-2009).]
