Bersaglieri

Perhaps I missed this info during my search, but here's a quick run down.

I have a 450hp LT1 to go into my Corvette. It's currently in a Fbody I'm returning to stock. The Fbody has a Ram HD clutch kit and Hays Billet Flywheel. I'd like to swap the clutch stuff over with the motor, but I'm reading this:


[In stock form, the ZF6 uses a "Pull style" clutch, similar to the LT1-T56 transmission. The only difference is,
a ZF6 does NOT use a sprung hub clutch disc, but rather uses a dual-mass flywheel with integrated springs between
the mounting surface and the friction surface. The OEM flywheel sells for nearly $700 US.

There are a few options for clutch replacement, other than stock. For example, you can change to a singlemass flywheel
and re-use a OEM type ZF6 clutch kit, OR use fbody clutch components, OR convert to a push style clutch.

1) If using a Singlemass T56 flywheel out of a 93-97 V8 Fbody (OEM# 10125379), you can use a Fbody sprung hub clutch disc (OEM #12551309),
but must use the propper ZF6 pressure plate for your transmission. Additionally, the flywheel must be resurfaced .090" for clearance
with the clutch fork to bell housing. This will only work on 1986+ motors with 1pc rear main seal!]



I also read this from gtsyellow:

[When it comes to the pressure plate and throwout bearing, stay with the ones intended for the Corvette. They will fit to these flywheels fine, and will work with either the Corvette or LT1 Camaro clutch disc.]

But neither place does it state why the Fbody pressure plate can't be used. I know the Fbody LT1 and Corvette LT4 pressure plates are interchangeable, so wouldn't the Ram Fbody one interchange as well?

Here is exactly what I have:

http://www.summitracing.com/parts/ra...maro/year/1995

http://www.summitracing.com/parts/ha...make/chevrolet

Thanks, Dustin.

nickgost

The problem with using a standard single-mass flywheel on a LT1 is that the engine is very sensitive to vibrations. You can use it, but I don't recommend it. The dual-mass floats on a big rubber bushing to stop these vibrations. If you don't use it the car will be rough to drive on the road, and the noise and vibrations will be quite annoying in neutral. So yes you can use that flywheel, but no I wouldn't.

96GS#007

The single-mass flywheel works fine. There are hundreds if not thousands of people running this setup with their ZF6 / LTx combo.

There is no more vibration than what you have with the dual-mass. The rear of the LT1/4 is externally balanced. In other words, the balance weight is on the dual-mass flywheel (it's cast in). Aftermarket single-mass flywheels come with a bolt-on weight to replicate the dual mass. In the pic below you can just make out the cast in weight on the right side of the dual-mass towards the edge (circled in red). The bolt-in weight is also shown on the single mass flywheel.



Since OP has a modified engine, in all likelihood, the engine is internally balanced and is neutral. In that case, the external weight on the single mass flywheel should not be used and can be removed by unbolting it as you can see here:



Properly balanced, there is no more vibration than normal.

The sole purpose of the dual mass is to prevent ZF6 gear rattle due to the gear cut the transmission uses. With a single mass flywheel and the clutch "out", transmission in neutral, you will get some pretty annoying rattle...often referred to as sounding like "rocks in a box". If you have an aftermarket exhaust, the noise is less noticeable but still there. This is true even if you use a clutch plate with a sprung hub. You will also hear some noise in 1st or 2nd gear is you lug the engine.

The benefit of the single mass is reduced weight which allows for faster revs. In addition, finding a dual mass to use is quickly becoming challenging at best and typically costs an arm and a leg.

WVZR-1

Jim,

I thought his question was regarding the pressure plate and I didn't see a Ram application for an LT4 Corvette anywhere in their application charts that specified a "pull situation". Everything I saw was a "push conversion" in Ram.

I thought the flywheel was already assumed by the OP. It seemed to me the question needed to be directed to RAM regarding their products.

96GS#007

My apologies. for clarity I was responding to the comments made in the 2nd post.

I'm not familiar with RAM products. I would call them directly. Several people have used the f-body flywheel with a ZF6 by machining it .090, but I don't recall what clutch components were used. A search on "F-body flywheel conversion" may yield some results.

Bersaglieri

I appreciate the explainations, but yes, it's all about the pressure plate. I'm aware of the typical information, but I'm yet to see anyone address the pressure plate, it just says "use the stocker". Over on LTXtech.com it was mentioned that the throw out bearing was different, but it's thought the pressure plate maybe the same.

I talked to Ram already and the guy wouldn't touch most of my questions with a 10 foot pole. The only one he did answer was that if I used the factory Corvette pressure plate the clutch kit would not be able to hold the power it was intended to and possibly damage the clutch.

I also called Hays about the flywheel and machining it .090" and it's balancing method. No one in the "office" new about how much it could safely be machined, etc, so he referred my questions to the "shop" and their supposed to be calling me back.

Hope that explains where I'm at.

WVZR-1

So it actually looks like you need to start from scratch and that would be with the flywheel. I'd guess that first of all you need to establish the height/thickness of the flywheel you have(from the mounting surface to the face of the flywheel).

Is your Corvette disassembled yet? What year and which trans? I'm guessing LT1 and a ZF? That's far enough I guess until you answer that. There's no need for guessing!

Can someone with an LT1/4 dual/mass post the height/thickness of the dual/mass mounting flange to crankshaft to the finish face of the flywheel? I can't I don't have an LT1/4.

Bersaglieri

Yes, I've got a 1995 LT1 Corvette with a ZF6. I'm pretty sure its a factory blue tag. [For whatever reason I can't get a signature to show up]

It's not taken apart yet, I'll probably start doing that today after work. I can measure the factory spacing/thickness as I'm taking stuff apart. I was just trying to get a jump on lining up parts if I needed to.

There is a guy on LTXtech who is putting a ZF6 into his Trans Am, so it looks like we're both working towards the same goal and also both stuck at the same cross road.

WVZR-1

How did you arrive at this? Where can it be documented? I can't say it's NOT so BUT...

Bersaglieri

I read alot of people using them over the years on CZ28. Back when the LT1 and LT4 pressure plates were different, it was claimed the LT4 design had more clamping pressure:

Our sticky on clutches, etc: http://www.camaroz28.com/forums/driv...ptions-520404/

Thread on the throw out bearing: http://www.camaroz28.com/forums/driv...estion-702831/

and: http://www.camaroz28.com/forums/driv...estion-586333/

and: http://www.camaroz28.com/forums/driv...please-462445/

and: http://www.camaroz28.com/forums/driv...e-disk-454355/

Just some examples of people running the LT4 pressure plate and throw out bearing. Now, they work in the T56 with no problem, so you would think it'd also work the other way around. At least I hope so, lol

Dustin

Bersaglieri

Also found this one from 2005: http://www.camaroz28.com/forums/driv...s-same-351832/

Claims they swap...

EDIT: Pictures of pressure plates

LT1:



LT4:



Aftermarket [SPEC]:

mn_vette

When I did a clutch in my zf6 the company sent me the wrong pressure plate, it was for an Fbody. It took me about an hour of messing around trying to figure out why the trans would not mate up. I called the company and they sent me just a corvette throw out bearing. I swapped the two and it worked great, never had any issues.

Bersaglieri

Good info, do you remember if it was an inside diameter problem, fork issue..?

mn_vette

It was the inside diameter, the ZF6 shaft is thicker than the Fbody

WVZR-1

I believe it's a combination of both - the Corvette release is the "squared w/corners cut" and an F-body is "round". Then of course there's the diameter of the "guide tube" (ZF terminology) vs that of the T56. The LT1/4 ZF '95 & '96 should have a 1.305" guide tube diameter. On the ID tag the last three digits should be 084 or 089. Something other than that it would require a confirmation. The front bearing retainer diameter of the T56 I'm unsure of.

Bersaglieri

Now we're gaining traction! Thanks again for that info.

Do you guys know where to find factory replacement ZF6 throw out bearings? I'm not sure it'd be wise to reuse mine with 165,xxx miles.

Looks like I'll try .090 off the flywheel [or should I just cut it enough to match the installed thickness of the factory dual mass?] and a ZF6 throw out bearing.

WVZR-1

I wouldn't rush into the cut of the after-market yet. The comment the way I read it was "when a GM LT1 flywheel was used" - that's why I suggested the measurement and comparison. You kind of need to disregard all the published Internet information and base yours on what you can actually measure and confirm. There's many comments around that there are only "off-shore" replacements available for the ZF style release bearing. I can't confirm that but I do know that they've been difficult to source. Are they "junk"? Can't comment on that either - there's many that create there own situations and it's nearly always blamed on the part. YMMV!

***
1. With the Corvette parts bolted together measure from the mating surface to the crankshaft to the fingers of the pressure plate.

2. Bolt the parts you want to use together and measure from the mating surface to the crankshaft to the fingers of the pressure plate.

3. Compare (allow for the thickness of a new disc)

Bersaglieri

I agree, after my last post I sorta told myself to slow down before I trip up on my ambition. That's good guidance on the measuring side of things. I'm a hands on guy so it was difficult trying to figure out where to take measurements from without having the parts in font of me.

How cautious should I be about reusing my high mile TOB? What about a lower mileage used one? I'll be looking for a new one today, but as with many other things these days, it might be better to have a used USA TOB vs a new China made one.

856SPEED

I have done the ZF6 clutch issues even though I am running a car never designed to run the ZF6. I can tell you from the school of "lessens learned" however.

First off, a single mass FW (which I run aluminum one from Fidanza) is one of few options; they have single steel mass FW's out there as well that are heavier, but may make the ZF a little quieter. Any yes, I can tell you from experience the f-body FW needs to be machined down to .090"...trust me I know! The car won't even start if the FW is machined for an f-body....taking it all apart again is rather fun

Spec makes a great high performance clutch (kit) for these cars when you explain your application to them and how the car is utilized (daily driver, hp/torque ratings/racing/etc.). I am not sure I would play with the pressure plate from an f-body; may work but why not put the intended pieces in there for the 95 manual?

I can tell you this transmission/clutch requirements on the Corvette C4 applications do not allow for a large margin of error. I recommend calliing SPEC and telling them what you have and what you want.....

96GS#007

Contact Power Torque Systems. He's got a bunch of original TOBs as well as other ZF6 clutch components.