Which type of flywheel?????

[vetteme1]

I have a '96 LT-4 & it is time to relpace the clutch. Since it has to come apart anyway, I thought I would go ahead & replace the flywheel. I have lined up a RAM clutch, & pressure plate & after reading some posts about flywheels, I was wondering about differences between the Fidan...aluminum flywheel & a steel flywheel (not going back to the factory type). I have not done any major tricks to up the pony power. I have "heard" that when you go w/aluminum that there is a "chattering". IS that true? Then there is the balancing issue. Shouldn't they come already balanced??? One of the main reasons I WAS leaning toward the Fidan.. flywheel is that the surface could be replaced the next time w/o replacing the entire flywheel.

Please let me know the pros & cons of both. Thank you (everyone) for any input.

 

[Aurora40]

I'm no flywheel expert. But I believe the noise comes from the change from dual-mass to single- mass, not the material of the flywheel. The Fidanza flywheel should be balanced, though. But no engine runs perfectly smoothly, and apparently the ZF gearbox is sensitive to vibration in that it makes noise. From what I understand there is no danger, just annoyance. You might try to hear someone else's car with a ZF and a single-mass to get an idea of what it might sound like.

 

[stgry1]

vetteme1, callaway corvettes offers a nodular iron SM flywheel pre-balanced for the LT4. I did a lot of research and went this direction. Install is next week. The couple it with a centerforce DF clutch kit. You may be able to by the fywheel seperately. You will need to ck with them. I liked the compromise of weight on the FW. AW=13-14# billet steel=33# nodular iron=19#. You'll get faster revs and maintain some inertia needed for daily driving. Also you can turn it if need be. Let us know what you decide.

 

[vetteme1]

stgry1, thanks for that info.....I didn't know about that type of flywheel....please let me know how that install goes & how you like it after driving a few miles...also approx how much for that set up?????

 

[stgry1]

The kit is approx 1K + shipping. Includes FW, clutch kit, pilot bearing, TO bearing and needed FW/PP bolts. Will let you know how it goes

 

[vetteme1]

I am looking forward to hearing about it. With all the info I have been given, or dug up, I am now leaning toward the set-up you are getting.

 

[Louis Bartay]

I just spent $2000.00 having this done at Mid Cities Corvette Classics and the owner Jim Welch who has been doing this for many years said that if you changed from the factory duel mass flywheel your ZF 6 speed when at idle and clutch out will sound rocks rolling around in the tranny, if your LT4 is not over 400 RWHP Do go back with the Factory duel mass flywheel ($1000.00) one the members of Cowtown Corvette club went with Findanza set up and it works Great but it sounds like rocks are rolling around in the tranny. I like mine quiet. E-mail www.zfdoc.com and see what Bill has to say(he is the North American ZF Factory rep) about it and DO replace the clutch master slave and bleed it like he has described on the site.

 

[CAJUN C4]

vetteme1, callaway corvettes offers a nodular iron SM flywheel pre-balanced for the LT4. I did a lot of research and went this direction. Install is next week. The couple it with a centerforce DF clutch kit. You may be able to by the fywheel seperately. You will need to ck with them. I liked the compromise of weight on the FW. AW=13-14# billet steel=33# nodular iron=19#. You'll get faster revs and maintain some inertia needed for daily driving. Also you can turn it if need be. Let us know what you decide.

Chris: How did the Flywheel Install go.Is it quite or noisy?
Plese let us know.

 

[stgry1]

Well I did a write up about it on the GSR. Feel free to read this link. http://www.grandsportregistry.com/forum/index.php?showtopic=1563

Now a follow up to that 500 miles later I will add:

The clutch kit materials/discs etc tolerances have changed slightly due to break in and i'm starting to hear more and more gear rattle. Mostly when it's warmed up and has been running for a while. Also I'm noticing more noise under hard accel. ALL normal characteristics when going to a SM. I was real happy and optomistic at first when I didn't hear anything but as time has progressed, I have to admit it is more noticeable now. I am still happy with the choice and would do it again but just prepare yourself for some harmless gear chatter. Some people claim they NEVER hear this after they have done the SM changeover but I am being perfectly honest with you and telling you that the chances are greater YOU WILL experience it. The cost and performance gain made it worth while in my book. Hope this helps.

 

[Louis Bartay]

Chris,
I wish you would have had your LT4 on a Dyno before you did the clutch and flywheel change. I would like to know how much H.P. gain this set up Really gains. I almost went with a SM flywheel but I just could not stand to hear the gear noise. One of the members of CowTown Corvette Club had his done and I heard the rock sound and went back OEM and spent $2,000.00 parts and labor :-( Next clutch that goes in I may have the Headers and a Cat Back exhaust so loud that I will not hear it.
Louis

 

[stgry1]

Louis. I DID have it on the dyno prior, I just haven't made it back yet. Once I return tho, I will have added other mods than that. To the list will be a 52mm TB, Shorty headers, and a custom LT1 edit tune, so the "true" gains of just the SM will not be accurate. I will state to you tho it really doesn't 'add' HP but free up exsisting HP as well as weight loss which in turn aids in the overall HP ratio. I'm sure you already knew that since you have been down this road before. But I really enjoy having less weight hanging on the end of my crank and the smoother, quicker revs I now experience.

 

[Louis Bartay]

Chris
I did the light flywheel on a 350 HP 327 back in the 70's and I noticed at the Dragstrip I had to launch at a Higher RPM with the lighter FW as the steel, heaver flywheel made my 65 Chevy II launch easier but it did rev faster with the lighter one installed. I only ran a 10th of a second quicker( 13:10@105 MPH) with 4:11 gears and the light FW. But it did feel like I shifted sooner at Redline. But that was more years now than I want to own up too .Do post what your LT4 does on the Dyno.
Louis

 

[96CERon]

Here is some info. I did all the work myself laying on the garage floor with a transmission jack from Harbor Freight. AND, I GOT TO DO IT TWICE. I used the Carolina clutch stage 2 kit. When I asked Carolina Clutches before I spent the $900 for the kit, Tom said that the flywheel and pressure plate were individually balanced and should go right in without a problem. There was a caution label on the flywheel that said you need to match balance the old one and new one, but assuming that Carolina Tom knew what he was talking about, I ignored it-- Bill Boudreau at ZR51 Performance, says "these engines required post assembly balancing via variable weights added to the flywheel and some were very difficult to get balanced. Dave (Tech support at Fidanza) confirmed that you have to match balance his flywheel to the dual mass unit. He said that they build these with a nominal (mid point) balance job but if the original balancing was at either end of the spectrum you must match balance flywheel to the old dual mass flywheel. I really didn't enjoy taking it down again and getting it match balanced. Sure enough the balancing was off by 30 gms. This is a tremendous amount at RPM-->100 pounds. I had another problem which was that the clutch disc from Carolina was miss-stamped as to which side is the flywheel side. On a "regular" car the clutch disc springs stick out more to the transmission side, but with this conversion the springs go the flywheel side but unfortunately the part was metal stamped incorrectly. You can put the clutch assembly together wrong, but the transmission will not go all the way together because of the input shaft cover hitting the backward clutch disc. Another thing, when I took it back down to do the match balancing, I found that the flywheel bolts and washer provided by Carolina were of poor quality. i.e. the washer were soft and the bolts really had no shoulders near the heads and therefore the washers and holes in the aluminum flywheel where deformed as well as the area under the washers was concaved. This could be a long-term problem with the flywheel coming loose over time! You must use hardened washers and bolts from ARP actually Summit--I believe these are the numbers-- bolts 200-2807 for $15.99 and washers 200-8539 for $8. Call ARP and verify. I also used the beam plates from ZFDoc. It makes taking the beam up and down much easier. Also make sure you mark the drive shaft relationship to the rear axle yoke so you can put it back in the same position.

I have no drivability problem as reported by some. I take off just fine with no more issue than when it was stock. I can take off in second gear if I want to. It does have gear rattle in neutral at idle. The engine pulses cause the gears to clatter back and forth--goes away at higher idle speed. I just say--racing transmission! I also get a resonance under heavy load--lugging from about 1K RPM to about 2K RPM--some say it is the resonance of the clutch springs--who knows but whatever it is you can drive around it and there is no problem in 6th gear. I think a lot of the noise issue is the hard mounting of the transmission to the beam and to the rear axle. It is a great amplifier. Do put in the 10-60 BMW oil in the transmission. It helps a little and is the best. I tried all different types.

Here is what theory says regarding the rotating weight reduction and resulting virtual weigh loss and rule of thumb horsepower increase and therefore faster acceleration. It is a function of overall gear ratio—i.e. this is for 3.54:1 rear axle ratio:

Gear 1 2 3 4 5 6
Mass Reduction in pounds 303 203 116 80 56 39
Equiv HP gain 30.3 20.3 11.6 8.0 5.6 3.9

I don't mind the noise I like the improved acceleration.

 

[stgry1]

Very nice write up Ron. I appreciate your time and efforts here. I concur with you on all aspects of the flywheel swap etc. Really sorry to hear about your dealings with Tom @ CC. I have talked to him in the past when I was considering the install and he was very helpful. I just wasn't convinced with using an AW flywheel. I opted for the nodular Iron from callaway and probably paid too much :L but I am satisifed with it. I'm sure I don't have the rotational gains that you have but at 19.5lbs, my FW is only a bit heavier. You didn't mention a short throw install while the trans was out? Would have been a great time for it. I love my Hurst...huge difference!
As far as the oil goes, I'm currently running the redline MT fluid and was thinking of trying the BMW or MT-90 weights to help with the noise. If you say it's worth the change, then I will put it next on the list

 

[96CERon]

The short throw shifter from ZF Doc would have been nice. As far as trans oils--tried them all from Redline Synthetics, etc. I think it was 75W-90 all the way up to 75-140--Only quiet when cold in the mornings otherwise no better than the 10w-60 from Castrol/BMW. The thicker oils did exhibit what I believe was a lack of initial lubrication when cold on start up in the morning--- resulting in a disturbing squeel that sounded like a seeve bearing without proper lubrication and cold shifting resistance. Went away after put the 10W-60 back in it. Which by the way is the recommended oil from ZF. Stick to the 10W-60 and change it once a year. I got it down where I can change the oil in less than 30 minutes.

 

[Louis Bartay]

Very nice write up Ron. I appreciate your time and efforts here. I concur with you on all aspects of the flywheel swap etc. Really sorry to hear about your dealings with Tom @ CC. I have talked to him in the past when I was considering the install and he was very helpful. I just wasn't convinced with using an AW flywheel. I opted for the nodular Iron from callaway and probably paid too much :L but I am satisifed with it. I'm sure I don't have the rotational gains that you have but at 19.5lbs, my FW is only a bit heavier. You didn't mention a short throw install while the trans was out? Would have been a great time for it. I love my Hurst...huge difference!
As far as the oil goes, I'm currently running the redline MT fluid and was thinking of trying the BMW or MT-90 weights to help with the noise. If you say it's worth the change, then I will put it next on the list

Thanks Ron
I will try the BMW oil as I have read several posts about it and I havetalked to Bill about it abd the dreaded clutch slave seal installed backwards.

Chris

How hard is the Hurst shifter to install with the ZF in the Vette??

Louis

 

[stgry1]

Chris

How hard is the Hurst shifter to install with the ZF in the Vette??

Louis

Well, that depends on who you ask. If you have acess to a shop and a lift, not too bad. If you're doing it from home, could be a PIA. Nothing like my old 93 cobra SC, couple nuts and screw the new one on :L I wish you didn't live so far, I'd be glad to help you out.