Someone asked in the not too distant past if there is a difference between the 4 and 5 speed clutches. I can now definitively answer "YES!"

THe height of the 4 speed pressure plate, as measured to the fingers is 2-3/32"

THe height of the 5 speed pressure plate, as measured to the fingers is 1-25/32"

That's a difference of 5/16", which is pretty significant in terms of clutch travel.

There is no difference is clutch plate thickness.

There is a difference in T.O. bearings, but I don't have a 5 speed one to compare to.

So, a 5 speed clutch/pressure plate in a 4 speed transaxle will result in not enough pressure plate travel, and shifting difficulties.

A 4 speed clutch/pressure plate in a 5 speed transaxle will result in severe slippage.

Additional stuff:
The old style clutch lever cannot be welded and expected to last:

I have ordered a new one from The Fiero Store.

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Mid Atlantic Fiero Owners Association
Keystone State Chapter, P.O.C.I.
P.O.C.I.

Hey Denny!
Looks like you now know the difference by experience...

So who did the welding?
Did they grind a valley initially?
Did they aneal afterwards?

Looks to be a good bead, but it fractured at the edge of the bead, making it look like the metal was under stress, and lacked anealling...
crash...

quote Originally posted by Fierowrecker: Hey Denny! Looks like you now know the difference by experience...

You bet!

quote So who did the welding? Did they grind a valley initially? Did they aneal afterwards?

Shop where my brother-in-law works.
He said they did.
I doubt it.

quote Looks to be a good bead, but it fractured at the edge of the bead, making it look like the metal was under stress, and lacked anealling... crash...

I don't doubt you a bit.

The ones from The Fiero Store are the new style, should hold up just fine.

THanks!

So what is the correct clutch for an Isuzu 5spd and V6 flywheel? 4spd clutch? Getrag clutch? Cause an Isuzu clutch doesn't work very long.

The only way to answer that would be to measure all three trannys. I don't have them to compare, maybe someone out there does?

Terry,
let me know if you need measurements, I have at least one of each type of trans sitting in the shed.

Jon

Thanks for the info

quote Originally posted by terryk: So what is the correct clutch for an Isuzu 5spd and V6 flywheel? 4spd clutch? Getrag clutch? Cause an Isuzu clutch doesn't work very long.

Getrag clutch and pressure plate with Isuzu T/O bearing. Works flawlessly. The tiny Isuzu clutch will slip. Use either the Getrag or the 4 speed setup.

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"Its a Fiero thing... Heck, even I don't understand!"

Timothy E. Smith
1986 SE V6 BACK ON THE ROAD AGAIN!!!!
1984 Coupe
1996 Ford Probe GT
1999 Chevrolet Silverado Z71
1975 Chevrolet ElCamino SS

Wait a sec. I've got a friend who just swapped a 5-speed Getrag for a 4-speed V6 Muncie in his 86 GT after a trans failure. He says it worked perfectly without changing the clutch. Denny, when you say 5-spd, are you talking about the 5-spd Isuzu?

Dave

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- Silver '88 GT 5-speed (1 of 139) w/cammed 3.4
- Black '88 GT 5-speed LS1 at Archie's
- '87 & '98 Corvette Coupes

Nope, Getrag.

The clutch/pressure plate I had in there was given to me, and I used it without knowing any better. It was a Summit clutch for the Getrag.

The Getrag pressure plate is 5/16" shorter (Z height) than the 4 speed. That 5/16" is extra distance that the hydraulics must move before exerting pressure on the pressure plate fingers. End effect is the clutch doesn't disengage fully, and grabs very close to the floor.

Using a 4 speed cluch in the Getrag would cause the clutch to engage near the top of the pedal's travel.

How it worked perfectly for your friend is something I can't answer.

I just swapped in a rebuilt engine and at the same time I replaced the clutch on my 4 speed with a 5 speed Isuzu clutch. Never thought to check the pressure plate.. The actual clutch is physically smaller in diameter than the 4-sp. But it works like it was made for it..
Haven't had any problems yet..(625 mi. on it)

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'84 SE-for Sale
'84 SE (Strictly Parts Car)For Sale W/other
'85 SE
'86 SE (soon to be Fastback SE)
'99 K-1500 Z-71
'00 HD 1200XL Sportster

To get any meaningfull measurements on the finger height the measurments have to be made with the pressure plate installed on a new clutch. When instaled on a new clutch the fingers lie almost flat. When I swapped the transmission on my 86 from a Isuzu 5sp to the Muncie 4spd I had two complete assemblies I could compare and the installed finger height was +- 1/16".
The biggest differences between the two throwout bearings were the ID of the bearing and the 4 speed bearing has a flat face where it contacts the release fingers, the 5 speed bearing has the rounded, self centering face on it. I believe the Getrag throuwout is also a self-centering bearing.
The fingers on the five speed pressure plate have a small curve at the end where the round face sits in, the four speed pressure plate fingers are flat on the end. I was going to use the 5-speed clutch with the 4-spd transmission but I was worried that the contact area between the between the fingers and the bearing would be to small or in the wrong place but it sounds like it is working O.K. for kyote.
If the hydralic system is working correctly the slave cylinder has enouge travel to "self adjust" out any small differences in installed height and the clutch should engage at about the same pedal position for the available clutch combinations.
The five speed Isuzu clutch has substantially less surface area than the 4 spd clutch and is more likely to slip under power.
The clutch arm is a crappy design and is to thin in the area where it cracks. Unless you build up the whole area to make it thicker it will crack again. Easier and more reliable just to buy the new arm.

Paul

Paul,

That's great to know, but I'm talking about the Getrag vs. Muncie here. That's what I was up against, and it didn't work very well.

I appreciate what you're saying about mounted measurements, but measuring on a flat surface can be accurate, too, if the pressure plate face height is known. In my case both pressure plates are the same height (distance) from the surface, so any measured differences are valid, no correction factor needed.

If you'll notice in the pictures, both pressure plates are used, so the bearing contact surface is easily visible. I used a small t-rule to measure to the bearing contact plane, which I think results in valid measurements.

Also, I now have the new RAM clutch from TFS, and the finger height on it is 2-1/32", and the pressure plate face is about 1/32" higher than the old 4 speed and 5 speed one.

Anyway, I'm trying to clarify here, thus also trying to understand why things didn't work out. Any and all input is welcome.

Denny,

I missed the part about it being a getrag 5spd clutch.

I undertstand how you are measuring the distance, I saw a similar difference on the Isuzu/Muncie pressure plates from my cars but when I bolted the assemblies together, side by side, the installed finger height was almost identical. Maybe the getrag is different? I don't know.

So you had a muncie 4 spd and throwout installed with a getrag pressure plate and clutch plate, and the clutch would not fully disengage, right?

What year car and tranny?

Paul

Paul,

S'okay, I do it all the time. Think it has something to do with the society we live in.

Anyway, that's correct, Getrag clutch and pressure plate, 4 speed T.O. bearing.

BTW, the clutch discs are the same thickness.

Also, the clutch lever being broken (twice) doesn't help the situation, you give up another 1/4" of travel (measured at the end of the lever, would be less at the T.O. bearing) there.

Little story here: I had the original clutch replaced (there's another story behind that one wearing out, but I promised to never embarass a certain someone with that) by a local transmission shop. Not only did they replace ONLY the clutch disc, and put a POS in at that, for some stupid reason they took the clutch lever off, then over-tightened the pinch bolt when they put it back on. Broke the lever.

So, I now do all my own work except paint, welding (no welder), and alignments, and machining.

[This message has been edited by Denny (edited 03-21-2002).]