Adapting Small bore slave to a Getrag,

 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 SC37995 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.  

Argh!

Got my new slave in from the Fiero Store this morning.  $89 US.

The Getrag was listed at $177 trade for some reason, at my local shop.......

Rotors I've got, but hubs are pretty darned pricey for the 88!

The Toyota piston mod looks interesting. The projection from the base of the piston is shorter on the Toyota piston which means that it will bottom later and will probably need a longer pushrod, otherwise you might get too much slop and unless the boot holds the rod in place, it could fall out.

Maybe I should start looking at British parts - on the Jamaican (with T5 and 3.4 Camaro engine) I used a Triumph TR6 slave cylinder and made up a pushrod.  I'll bet it will also work for the Fiero....with suitable adaptor plate, of course. And it cost $40.

Capt Fiero wrote: The pedal is about 50% harder to push in as well. It will take a while to get used to the much firmer pedal.

Capt Fiero wrote: 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.

Hmmm... hopefully the "much firmer pedal" doesn't continue to blow master cylinders. That extra pressure (resulting from the smaller bore size of the new slave) just might be too much for the master cylinder seal to withstand.

Patrick wrote: Capt Fiero wrote: The pedal is about 50% harder to push in as well. It will take a while to get used to the much firmer pedal. Capt Fiero wrote: 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. Hmmm... hopefully the "much firmer pedal" doesn't continue to blow master cylinders. That extra pressure (resulting from the smaller bore size of the new slave) just might be too much for the master cylinder seal to withstand.

         Nope, I think everyone is aware how I drive my cars, and after a lot of extremely hard clutch pushes, rapid gear changes and hammering back onto the clutch, no failures of the master since I replaced the aging one that was in it.  It sure if weird going from my car to a car with a stock slave as it feels like a feather weight.  It actually feels like the pedal has air in it, LOL.