Clutch release arms

Series8217 · Post by **Series8217** » Mon Mar 27, 2006 8:04 pm

There are three different lengths of clutch release arms that fit all of the Fiero transmissions.

The Muncie 4-speed and Isuzu 5-speed use the same arm; the long one to the right in the picture. The Fiero Getrag uses the one in the middle. The FWD Getrag uses the one on the left. Note that there is also a stamped steel Isuzu and Muncie arm. These are known to crack and bend. Avoid them! Use the cast iron ones shown in the pictures here.
A few of the engine swaps (the Northstar and 3.4 DOHC come to mind..) have clearance issues with the release arms on the Isuzu and Muncie. In the case of the 3.4 DOHC the arm interferes with the exhaust crossover pipe, and in the case of the Northstar I think it hits the water manifold.

The lever arm length of each is as follows:
FWD Getrag: 2.4 inches
Fiero Getrag: 3.4 inches
Isuzu 5-speed & Muncie 4-speed: 4.875 inches
Note that this is the length from the opening for the shaft to the center of the pushrod cup measured from a projection of the arm onto a plane. The actual distance from the pivot to the cup is NOT the lever length because it rotates about the axis of the shaft.

Solving clearance issues or tweaking your clutch pedal effort isn't as easy as just putting on a different arm.. While the arms are interchangeable, the slave cylinder brackets are not, so the only way to use a different arm is to make a new bracket. It is NOT necessary to use the slave cylinder that matches the arm. You may have to change the pushrod size so that your slave cylinder doesn't bottom out or overextend, but even the Isuzu slave will work with the FWD Getrag arm. I've done it. The effort is very hard, and the clutch releases quickly, but its certainly driveable; it just takes some time to get used to it. I've also used the Fiero Getrag slave on the FWD Getrag arm. It improves the effort noticeably.
Today I'm building a bracket to locate the Fiero Getrag slave on an Isuzu 5-speed with the Fiero Getrag arm, so that the effort is the same as Fiero Getrag.. as long as the internal lever arm for the throwout bearing is the same length in all the transmissions, that is. If anyone knows about that please let me know.
Hopefully this information will help someone besides me.

crzyone · Post by **crzyone** » Tue Mar 28, 2006 12:25 am

Good post. I had to shave one side of the cup a bit to clear my waterlog on the N*. This was on a Rodney Dickman modified isuzu arm to fit a getrag. (Basically a cut down and welded cast isuzu arm for $60)

Shaun41178(2) · Post by **Shaun41178(2)** » Tue Mar 28, 2006 6:06 pm

I will concur. good post. Its good to see the difference between all 3 arms.

:thumbleft:

Kohburn · Post by **Kohburn** » Tue Mar 28, 2006 6:34 pm

and ofcourse there is always the stamped metal arm that i cut and welded to make it fit under the dohc exhaust

i also reinforced it significantly

donk_316 · Post by **donk_316** » Tue Mar 28, 2006 6:35 pm

Kohburn wrote:and ofcourse there is always the stamped metal arm that i cut and welded to make it fit under the dohc exhaust

i also reinforced it significantly

PICS! Cause i have the stamped arm sitting here too. Which was a "84 only" thing i think but its the same size as the other 4spds just made out of pieces of steel spot welded together, not cast like the newer ones.

Kohburn · Post by **Kohburn** » Tue Mar 28, 2006 6:36 pm

shit i dunno if i have one - i'll have to look

couldn't find any pics..

basicly made the arm back to remove the plastic end and welded an acorn nut on the end as the new pushrod seat.. this made it is short and lower (closer to the tranny) so that it cleared the exhaust just fine

Series8217 · Post by **Series8217** » Tue Mar 28, 2006 6:43 pm

donk_316 wrote:
Kohburn wrote:and ofcourse there is always the stamped metal arm that i cut and welded to make it fit under the dohc exhaust

i also reinforced it significantly
PICS! Cause i have the stamped arm sitting here too. Which was a "84 only" thing i think but its the same size as the other 4spds just made out of pieces of steel spot welded together, not cast like the newer ones.

84 and 85 had it I think. I don't have one but mentioned it in my post.. they are notoriously weak. If you end up using it, do as Kohburn did and reinforce it as much as possible.

Kohburn, do you have any pics of the slave bracket you made to fit the shortened arm? Or did you somehow modify in so that relocating the slave was unecessary?

Kohburn · Post by **Kohburn** » Tue Mar 28, 2006 6:44 pm

donk_316 wrote: Which was a "84 only" thing i think

dunno - i've had cast ones break too

but my 84 has a cast and the 86 has a stamped one go figure

Series8217 · Post by **Series8217** » Wed Mar 29, 2006 5:58 pm

I put the Fiero Getrag arm on my Isuzu and made a bracket for the Fiero Getrag slave. It's really sad how easy the clutch effort is now. I don't feel like a man anymore

I also have a shitty brand new aftermarket slave that I can't bleed properly because it just has the weak umbrella seal. Anyone have a junk Getrag slave they can part with? I just want to put this piston in this aftermarket bore with some new seals..

Kohburn · Post by **Kohburn** » Thu Mar 30, 2006 6:57 am

Series8217 wrote:
Kohburn, do you have any pics of the slave bracket you made to fit the shortened arm? Or did you somehow modify in so that relocating the slave was unecessary?

wasn't necessary to relocate the slave

Series8217 · Post by **Series8217** » Thu Mar 30, 2006 8:53 pm

Pics?

The Dark Side of Will · Thu Oct 08, 2020 4:22 pm

Series8217 wrote: ↑Mon Mar 27, 2006 8:04 pm
The lever arm length of each is as follows:
FWD Getrag: 2.4 inches
Fiero Getrag: 3.4 inches
Isuzu 5-speed & Muncie 4-speed: 4.875 inches
Note that this is the length from the opening for the shaft to the center of the pushrod cup measured from a projection of the arm onto a plane. The actual distance from the pivot to the cup is NOT the lever length because it rotates about the axis of the shaft.

How many SigFigs do you have in these dimensions? Did you take the measurements with CMM or calipers?

It occurs to me that putting the arm on a shaft facing the wrong way would let me measure the cup to the shaft directly with calipers.

Also, you don't happen to have the part number for the FWD Getrag external arm, do you?

Series8217 · Post by **Series8217** » Sun Oct 18, 2020 11:37 pm

The Dark Side of Will wrote: ↑Thu Oct 08, 2020 4:22 pm
Series8217 wrote: ↑Mon Mar 27, 2006 8:04 pm
The lever arm length of each is as follows:
FWD Getrag: 2.4 inches
Fiero Getrag: 3.4 inches
Isuzu 5-speed & Muncie 4-speed: 4.875 inches
Note that this is the length from the opening for the shaft to the center of the pushrod cup measured from a projection of the arm onto a plane. The actual distance from the pivot to the cup is NOT the lever length because it rotates about the axis of the shaft.

How many SigFigs do you have in these dimensions? Did you take the measurements with CMM or calipers?

Probably calipers. # of sigfigs unknown so I wouldn't assume anything beyond what I wrote in that post from 14 years ago. I found the directory I had the above image in, and it had more images but none with the measuring device or any other useful detail.

It occurs to me that putting the arm on a shaft facing the wrong way would let me measure the cup to the shaft directly with calipers.

Also, you don't happen to have the part number for the FWD Getrag external arm, do you?

I don't have the p/n for it.

I've been working on garage organization for the past few weeks so if I come across these arms again I'll re-measure them.

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