Intermittent growling and harsh vibrations in neutral

[1991 Corvette ZR-1]

Hello all. Recently, I have noticed an extra prominent growling, chatter or vibration while in neutral. I can feel it through the gearshift lever pretty well when it happens. Does not seem to happen all the time and does not occur when coasting in neutral from speed. I have mainly noticed it 20 seconds or so after startup and it lasts for about 5 seconds. Just came back from a drive and was waiting for the garage door to come up with clutch in and it did it again. Happens if using the clutch for neutral or leaving the gearshift in neutral gate and idling. Does not appear to be a thing that happens when in gear and at speed.

If I had to guess, it is dual mass related. 1991 with almost 93K miles. I am wondering if anyone else has experienced this? I am aware of the normal growling from black tags but this is not the normal frequency. I am planning a fluid flush of the trans next week and now I am considering replacing the clutch hydraulics just for safe measure. I committed a cardinal sin and only replaced a failing clutch master two years ago and left an aftermarket cast iron slave in place.

[1991 Corvette ZR-1]

Ugh just realized I put this in the wrong section. Mods, if you can move to the appropriate tech section.

[GOLDCYLON]

Moved :cheers:

[Great White]

Possibly a bad pilot bushing/bearing or throw-out bearing.

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[1991 Corvette ZR-1]

I see Corvette Central has the fluted pilot bearings. That is one piece of the puzzle. As far as a replacement clutch fork stud, because I know it will be worn and they are hard to come by. The fork, the TO bearing, these items will be tricky to find?and expensive. The dual mass is probably close to being toast. I was looking at an aluminum flywheel RAM clutch kit with hydraulic TO bearing on Jerry?s website not long ago. Sounds so much more hassle free to order that than try to wrangle all these rare parts together.

Anyone installed this kit?

https://www.jerrysgaskets.com/clutch-kit-ram-powergrip-single-organic-disc-89-92-28d1/

[tccrab]

Be forewarned, the lightweight aluminum flywheel can cause a very loud gear rattle that I've heard referred to as the box of rocks syndrome.
Just so that you're aware of it, and it doesn't come as a surprise.
I've read that there are certain tweaks to the idle speed that can help......a little.
The good news is that the lightweight flywheel will cause an immediate improvement on how quickly the motor will rev up, the bad news is that you'll be buying rear tires much more often.

Crabs

[A26B]

FYI
Not all single mass flywheels are featherweight (13~14lb).

Jerrys Gaskets had Ram Clutches make custom, aluminum billet flywheels in 18# & 22#. There are 2 principal reasons for these flywheels.

1. The heavier flywheel will mitigate/dampen engine impulse, the cause of transmission rattle. Not as effective as the DMF flywheel, but more than the 13~14# SM units. The 18# & 24# units are dimensionally identical to the OE DMF, maintaining the same clutch geometry, with the OE pull-release clutch.

2. The SM lightweight flywheels do rev quicker but do not develop the same level of kenetic energy as heavier units. More weight translates into easier launches during street driving as well as drag racing.

We do have some OE clutch components (fork & ball studs).

The push-release clutch can be used on all flywheels offered by Jerrys Gaskets.

[1991 Corvette ZR-1]

Thanks for the input, guys. Crabs, I have heard all about the rattle one can expect with the 13lb flywheel. I am wondering if one of ZF doc?s countershaft shims would help. I have one collecting dust unopened. I have also read some have applied brake quiet on the crank mating surface before bolting the flywheel on, but I do not think I would do that. I think the goal would be to go for the most free revving option, while I am in there but I would probably be happy with the 18lb version as well.

Jerry, on the RAM kit that includes the hydraulic TO bearing, are there any additional pieces that need to be picked up, such as shims or any other bits? Just trying to do my homework. Also, blue loctite: is there a specific formula number to use on the pressure plate bolts and flywheel to crank bolts?

[A26B]

.......... Jerry, on the RAM kit that includes the hydraulic TO bearing, are there any additional pieces that need to be picked up, such as shims or any other bits? Just trying to do my homework. Also, blue loctite: is there a specific formula number to use on the pressure plate bolts and flywheel to crank bolts?

Use RED Loctite 262 (high strength), not Blue/medium strength on all Flywheel & clutch bolts.

Read the full description for the RAM kit you are interested in. What is included and any other needed parts which are not included are specified.

[1991 Corvette ZR-1]

Use RED Loctite 262 (high strength), not Blue/medium strength on all Flywheel & clutch bolts.

Read the full description for the RAM kit you are interested in. What is included and any other needed parts which are not included are specified.

Red 262 works. So after some browsing, I believe I will stay with the pull clutch setup. I see throw out bearings are still available for the black tag and I have a fluted pilot bushing ordered.

A dilemma I am running into now is making all the other parts work. I would like to use an aluminum flywheel, 13lb version. Some pictures of Fidanza brand appear to show the flywheel not designed to accept a sprung hub clutch. For those who have gone the aluminum flywheel route: what sprung hub disk did you use and what brand pressure plate? Just trying to avoid sending parts back because that is never fun.

Aftermarket pressure plates require longer bolts but is there a particular brand or pack to purchase?

[Paul Workman]

I have the 13# Fidanza and sprung hub disc (Centerforce #381039 fm Summit Racing).
I'm running stock cams (re-phased a bit) w/ the idle set at ~ 1100 rpm. And, once I replaced my injectors (had a couple gone bad), it idles smooth and there is so little gear rattle that I hardly notice (1990 w/ black tag trans).

The combination of higher idle and sprung hub seems to be very effective at minimizing the gear rattle which is typical of the light weight, single mass FWs. But, on the other end of the spectrum, my wife Ami's 91 ZR-1 has Pete's cams and phasing and her's does idle like a box of rocks!

As far as normal (street) driving goes, I noticed the lighter FW a little at first - especially if starting from a stop on an up- hill start. But, w/in a very short time I learned to give it a bit more gas pedal - just a smidge - and never thought about it again. But, on the flip side, I love the snappy response to the gas pedal - especially in the first couple gears! (the rear tires often get loose with accelerator only in 1st gear - even w/ stock "345" rear gears!)

No regrets. I'd swap to the 13# Fidanza again in a New York minute! Some (especially those that drag race a lot) prefer the 18-22# version FW. But, my source of kicks from my Z are the twisties; that very snappy acceleration between and coming out of curves - call it responsiveness(!) - significantly adds to the thrills for this ol' man!

YMMV. I could suggest you maybe hook up with someone with the lighter FW and see how you like it. Ignore the initial reaction you get when driving on the street, b/c you'd very quickly adapt and never give it another thought. But, I think you'll like the responsiveness. And, the sprung hub and with a little more idle speed, I doubt you'll notice the increase in gear rattle (at idle with the clutch out).

PS: ALSO... I forgot to mention, I'm running the REDLINE HEAVY SHOCK full synthetic gear oil in the trans. That too takes a little bite out of the gear rattle.

[1991 Corvette ZR-1]

Paul, thank you for the information! If that clutch disc is good enough for your car, it should work just fine for mine. Did you reuse your pressure plate? I think the pressure plate and proper bolts for it are the final piece of the puzzle.

[Paul Workman]

Paul, thank you for the information! If that clutch disc is good enough for your car, it should work just fine for mine. Did you reuse your pressure plate? I think the pressure plate and proper bolts for it are the final piece of the puzzle.

Yes, I still have the stock pressure plate (which is unique to the ZR-1s).

[1991 Corvette ZR-1]

I would like to give an update and in doing so, I am sure I will jinx myself. Admittedly, I have been putting off doing a clutch fluid flush for a while now. I only really drive it on the weekends, so I never anticipated the fluid to be coffee colored from the driving I do. No clutch dumps, no burnouts, just the occasional WOT through a couple of gears. Everything else is tame cruising.

Got under the car, cracked the bleeder valve and let it slow drip into a pan while stirred up the bottom of the reservoir with a Q tip so all the old black fluid could flush out. Refilled with GM clutch fluid I have had for a few years now and happy to report after a nearly three hour drive, no growling when clutching in. Not a single episode at all and many many gearshifts during the drive.

That being said, I will still continue to acquire parts for the day I do have to change things out.

[1991 Corvette ZR-1]

Well, when you think things are too easy, they probably are. The fresh fluid helped my issue only temporarily, as the growling and shifter vibration is back. Only when the clutch is pressed in while stationary. I do not have any issues when at speed and changing gears. I am going to make a SWAG that it is throwout bearing related. Whatever it is, I have to go in there eventually. So it looks like my hopes of putting a clutch job on the back burner for a few years is no longer a thing.

Does anyone have a place they have picked up a throwout bearing from and had satisfactory results? I know the factory replacements are no longer a thing.

[secondchance]

Well, when you think things are too easy, they probably are. The fresh fluid helped my issue only temporarily, as the growling and shifter vibration is back. Only when the clutch is pressed in while stationary. I do not have any issues when at speed and changing gears. I am going to make a SWAG that it is throwout bearing related. Whatever it is, I have to go in there eventually. So it looks like my hopes of putting a clutch job on the back burner for a few years is no longer a thing.

Does anyone have a place they have picked up a throwout bearing from and had satisfactory results? I know the factory replacements are no longer a thing.

I bought a throw out bearing made by Centerforce. Although I have not installed it, visual inspection suggests it to be a quality product.
https://www.ebay.com/itm/234165909550?epid=252938682&_trkparms=ispr%3D1&hash=item368560382e:g:FcIAAOSwIiNhLc7T&amdata=enc%3AAQAGAAACsPYe5NmHp%252B2JMhMi7yxGiTJkP rKr5t53CooMSQt2orsSRAQR8FABHjfpFoyRlXhWmQehPkSOHV8 %252FgLU4W%252FHao1osbGVA9C1aK8dNdYe6Of02FbuZ8a9Q1 8Ielil5dGwNrpPHwR8mhxWMfyf9ona00%252Bvo7afRs7lnfoj 40CvOqDNWERROfeduLJz%252B5Gh%252Fg9i%252FKF3cu455% 252FsMqOfANKBeoCxUilTSrvjkVWesCD7Ivjew9Tr6YR%252Bo taEpSPOvPOSLHhwOz6b2QIYI8JUv5UvaPJ3eDEq8sc%252FzCp oE1Ut6kz7GwzpyUhkcZwdfiIOF3%252FUXuvgPN0T4bM1YydcA keeUesEnbFAOoL8026AWXvjcVjEciZ2henGRGgSrDIksGyGpOj 5mEqaqlfSNH4OMjg19sjZgS5b%252F5l5TBqd7qcJvn1839IkI YxEQ43PCb55Taax2xcAsLg296CNScvYi1t1JCo%252BVzJicuS 8jFeoBLClUzB0FuHQmtZmvmqiH8D4ZnmORREEtDsfzUWzY1uhU ezaSbvtGVbWmiymFTU0CVMqXHZGFyjj8h2S1pW5TRqqGhFqFzs H7il3LMEarCbxYo82HEiJQyeIgc%252Bs4bGmKHHp1ehjCY2hs O1W7ZxLuzB8lvAIj9zcnO43TiM1EzW%252Bb7GlH4EisQl9D5J %252BxB35of2mSLbQjTT4W3oYWAZVC6M402zB2brKmCXPO%252 B9fRD44Moqe3Dmc5oUy2nz1EeJ7Ew3qRDKOswZ4eJsDH4XXk1I LV90QLIluGWGza%252FYctjyJNCnUo7ticVTgRAHBPcQr%252B o12qHhGR%252BqRbL6M0fpWJNacp3SNm1pqP%252FX036CfQoD 2jGSPcOin%252Ba%252FBgoHeeuazu1BfSd7xUfKdG9cEXwe%2 52FhTFaHF7jeM4hjW2A3OZCsgDoiwV9poTjg%253D%7Campid% 3APL_CLK%7Cclp%3A2334524

[1991 Corvette ZR-1]

Secondchance, thank you for the link. That one specifies 94-95 TB, I will see if they offer a 90-93 black tag version. No clue when the fluted pilot bushing will be shipped that I ordered, if ever. So I have decided to go with pilot bearing CT1078, per Marc?s article on clutch replacement options.

[1991 Corvette ZR-1]

Ordered a Fidanza flywheel. Found one for a decent price of $354, a full $100 less than what every other parts place was offering them for. I did feel a little wary about ordering it from them versus a larger site like Jegs. Surprisingly, Jegs offers price matching AND I get up to 1 year to return the part unused if I decide not to use it. Seemed like a no brainer and here is the link to that site offering the Fidanza for $354 so if anyone wanted to price match it over at Jegs, they could.

https://rcagarage.com/shop/drivetrain/flywheels/fidanza-90-95-chevy-corvette-zr-1-5-7l-aluminum-flywheel-198551-31-2/?gclid=CjwKCAjw2bmLBhBREiwAZ6ugo5e4PdbBtIdUF-2KemTx2UKZUx-HwLI6DOaECR6lx5yMHcMq9JeauxoC5yEQAvD_BwE

Jegs offering


https://www.jegs.com/i/Fidanza/383/198551/10002/-1

Still researching my clutch disc options but looks like I am going with Jegs on this one, again mainly for the return option of 1 year, and ordering the Centerforce disc 381039:

https://www.jegs.com/i/Centerforce/183/381039/10002/-1

Guess I will just make this the thread for the journey of aluminum flywheel installation. I wish Marc or a ZR-1 competent shop was close because I do not enjoy clutch jobs on my back but it is what it is.

[1991 Corvette ZR-1]

I wanted to do a little follow up as I wait for parts to arrive, I may have isolated the issue. The growling and shifter vibration appears to happen the most when letting off the clutch pedal. So taking off from a stoplight gives the most noise as I ease off the pedal while applying gas and when shifting from first to second, I don?t hear any noise but I feel the faint growling transferred through the shifter. Same for any other gears. Not happening every time though. At some lights, it is embarrassingly loud, other stand still starts, nothing but normal operation.

Marc has been a tremendous help in the information provided in his articles. I did not see the McMaster-Carr part number returning a search result on their site. If I Google it, the only items that populate are Marc?s article and a thread on this site about it. I found this for the .005? thickness to shim the pressure plate feet to clear the Centerforce disc.

https://www.amazon.com/005-Thick-Stainless-Steel-Stock/dp/B006D1JNV2

Parts so far:

Fidanza Flywheel 198551 - shipped but delayed
Valeo throwout bearing - on the way from ZF Doc
Centerforce disc 381039 - on the way
Pilot bearing CT1078 - Acquired
ZF Doc countershaft shim kit - Acquired
Flywheel bolts - not sourced
Pressure plate bolts - not sourced

Just listing it out in case someone in the future thinking of doing the same thing might come across this info and save some time. I am about 93,300 miles on the odometer, so not sure what the pressure plate condition will be if I can reuse it. Part of me wants to just buy a new L98 plate and deal with the reduced clamp force instead of waiting to get everything apart, realize the factory unit is no good and wait longer for new parts to show up.

Is anyone using the shorter pressure plate? I am not making crazy power by any means. It is just the usual ported top end, headers, exhaust and 3.90 gears.

[1991 Corvette ZR-1]

Flywheel showed up. From reading the instructions it is an
AS IS product. Expected, but surprised by how much of the paperwork is dedicated to holding Fidanza harmless to part malfunction. I know they make a lot of different flywheels for all kinds of cars, so understandable. I have never read any posts from ZR-1 or C4 owners complaining about the durability of the product, so I am comfortable with using it.

The steel friction surface does not have the green coating. I figured they all do, as I have seen pictures of these exact flywheels with the coating. There does appear to be a scratch on the plate surface about an inch in length. If I drag my fingernail over it, it catches. It is not horrible, at least to me, but figured I would ask if that is a concern. Attached a few pictures.

[1991 Corvette ZR-1]

The pieces are slowly coming together. So a link from a previous thread for SRP extended length bolts is no longer available. Does anyone have an online source for proper length pressure plate bolts for OEM pressure plate to Fidanza?


https://www.zr1.net/forum/showthread.php?t=8306

The remedy for ?combo 2? on page 1 appears to be a dead link now.

[A26B]

I have ben able to call ARP & talk to an engineer, give them the dimensions of a particular bolt, and they could find it, when it doesn't show up on a website catalog. The only difference is the thread length. If you have even a picture of the extended length bolt, you can count the number of threads. Each thread is 1/16". Or, since you have the FW, measure just the threaded length for the bolts, not the full thickness of the FW, from the surface.

[1991 Corvette ZR-1]

I have really been dragging my feet on dropping the trans but I wanted to post a link to a sale of ZR-1 clutch fork studs. I think five or so of these were left when I bought mine. Looks to be a stock that was left over from when Power Torque was still open for business online for C4 parts. I got one just in case. The seller also sent me an email on torque specs and procedure for installation. Very helpful so I figured I would pass this along for anyone who wanted to get one.

https://www.ebay.com/itm/153722652336?mkevt=1&mkpid=0&emsid=e11050.m43.l1123&mkcid=7&ch=osgood&euid=8a56edac4703446bb0d9f3dab8298f6d&bu=45131220897&osub=-1%7E1&crd=20211102111053&segname=11050&sojTags=ch%3Dch%2Cbu%3Dbu%2Cosub%3Dosub%2Ccrd%3Dcr d%2Csegname%3Dsegname%2Cchnl%3Dmkcid

[HAWAIIZR-1]

I have really been dragging my feet on dropping the trans but I wanted to post a link to a sale of ZR-1 clutch fork studs. I think five or so of these were left when I bought mine. Looks to be a stock that was left over from when Power Torque was still open for business online for C4 parts. I got one just in case. The seller also sent me an email on torque specs and procedure for installation. Very helpful so I figured I would pass this along for anyone who wanted to get one.



https://www.ebay.com/itm/153722652336?mkevt=1&mkpid=0&emsid=e11050.m43.l1123&mkcid=7&ch=osgood&euid=8a56edac4703446bb0d9f3dab8298f6d&bu=45131220897&osub=-1%7E1&crd=20211102111053&segname=11050&sojTags=ch%3Dch%2Cbu%3Dbu%2Cosub%3Dosub%2Ccrd%3Dcr d%2Csegname%3Dsegname%2Cchnl%3Dmkcid



Thanks for sharing. You are right, that is Jim Jandik (great guy) and I wish he didn?t retire, but we all gotta do it some day.

I hope you get the trans sorted out and not a big issue. [emoji1374]


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[1991 Corvette ZR-1]

Alright, guys I am finally dragging my sorry butt out to the garage to do this. She is up in the air on jack stands. Trans oil drained, exhaust removed. Interior bits removed from the console and shifter. If I remember, the shifter needs to be in 3rd. I have a ZF Doc short shifter installed, so that should make removal a little easier. I think I need to remove the MAP sensor and let it hang free from the back of the plenum. The air filter accordion has been removed.

Does anyone have the part number for the Redline Shockproof transmission oil? I see this:

https://www.amazon.com/Red-Line-58205-Heavy-ShockProof/dp/B000J3K0OY/ref=asc_df_B000J3K0OY/?tag=hyprod-20&linkCode=df0&hvadid=312151579877&hvpos=&hvnetw=g&hvrand=10411377782414339430&hvpone=&hvptwo=&hvqmt=&hvdev=m&hvdvcmdl=&hvlocint=&hvlocphy=9011562&hvtargid=pla-569006605679&psc=1


But I have also seen where some have run the Redline 75w-140, but it does not say ?shockproof? on the jug, so I am guessing they are slightly different? Just want to make sure I get the right oil. With the right oil, I am also installing a ZF Doc oversized countershaft shim, so these two combined should dampen the gear rattle.

Bye the way, what angle do you guys get the engine and trans to dip to before you start breaking loose your bolts? I believe I remember reading from Pete that the engine can hang free once the trans is removed.

[1991 Corvette ZR-1]

Just curious for those who have done this, how much of your shifter is still peeking through the trans tunnel before you attempt removal? Taking a break anyway after removing the C beam and tilting the engine trans assembly, so figured I would ask. I am running a shortened shifter by ZF Doc. At this rate, I might be done by Christmas!

Edit: Nevermind, she is out. I forgot how much fun this was on your back. I was going to install a new fluted bushing, but there is just no way I can get this back together and not get grease on the input shaft tip, passing through the greased TO bearing, before it seats into the bushing. I believe I am going to use the input bearing, instead.

[1991 Corvette ZR-1]

Found something that is not what I wanted to find. It appears to be parts of the input bushing on the tip. At least that is what I hope it is. Going to use a fine pick to see if I can remove it. Looks like the input shaft splines won this clash I hope?

[1991 Corvette ZR-1]

Guys, I am in a rough spot. Someone has been in here already and installed an input bearing that appears to have started to let go. Also, from the pictures, the bearing does not appear to have been seated at the right depth. I knew someone had been in here when I noticed the wiring harness for the connections on the trans were free from the clip up near the vent tube. The f*****g genius also used some type of impact gun and over torqued the bell housing bolts. I was only able to get three of the eight bolts free and that was with an electric impact good up to 300 ft lbs breakaway torque.

So? I am screwed. I need a more powerful impact that is not air powered. Any suggestions? I am not even sure what I want to do now, had to walk away and cool off.

Edit: looks like I am buying a DeWalt 20V Max XR. 1200 ft lbs of breakaway torque versus the 300 I have now.

[A26B]

https://cdn10.bigcommerce.com/s-nkg90o/products/879/images/2060/Pilot_Bushing_Relative_Position-B__59922.1484268600.1280.1280.jpg?c=2

[HAWAIIZR-1]

Found something that is not what I wanted to find. It appears to be parts of the input bushing on the tip. At least that is what I hope it is. Going to use a fine pick to see if I can remove it. Looks like the input shaft splines won this clash I hope?

Sorry to hear and see these woes. That input shaft tip doesn?t look right unless that is just angle of the photo. You might send the photos to Bill at ZFDoc for some input.

About the bolts, are you sure you cannot break them free with move leverage? Long torque wrench or pipe on the end? Damn, did they use red Loctite or something? Maybe some heat to the bolts? I would hate to put impact to it.
Best wishes.

[1991 Corvette ZR-1]

Thank you for the picture, Jerry. Craig, I got the bell housing off. I don?t trust myself with fire and I am positive I would have set something on fire trying to snake a bottle torch up the tunnel to the bolt heads. The engine surprisingly does not dip that much, so it was a tight fit.

Took my chances on a bigger impact. It worked! It was $575 of equipment but it worked. Milwaukee M18 half inch anvil impact gun. Got them out fairly easy with that one. More bad news, it appears to be an L98 plate and possibly knock off clutch disc. Fought the bell all day, so I will remove the rest tomorrow.

[HAWAIIZR-1]

Thank you for the picture, Jerry. Craig, I got the bell housing off. I don?t trust myself with fire and I am positive I would have set something on fire trying to snake a bottle torch up the tunnel to the bolt heads. The engine surprisingly does not dip that much, so it was a tight fit.

Took my chances on a bigger impact. It worked! It was $575 of equipment but it worked. Milwaukee M18 half inch anvil impact gun. Got them out fairly easy with that one. More bad news, it appears to be an L98 plate and possibly knock off clutch disc. Fought the bell all day, so I will remove the rest tomorrow.

Thanks for sharing and good news. What you said makes sense and I guess I have not been under there for awhile. Sorry to hear that you take one step forward and two steps back. The good thing is you will get it all sorted out right. I can imagine your frustration and best to take a break as you are doing.

[1991 Corvette ZR-1]

Thanks for sharing and good news. What you said makes sense and I guess I have not been under there for awhile. Sorry to hear that you take one step forward and two steps back. The good thing is you will get it all sorted out right. I can imagine your frustration and best to take a break as you are doing.

Well, Craig you drive a hard bargain! Why should I stop there tonight? Took the rest off. Hot spot city. The DM flywheel is pretty sloppy I have a feeling it would fail a quality check but it does have 93K miles on it so?.I guess it should be worn out? Not all these hot spots are mine. I got her with 81K on the odometer.

[HAWAIIZR-1]

Well, Craig you drive a hard bargain! Why should I stop there tonight? Took the rest off. Hot spot city. The DM flywheel is pretty sloppy I have a feeling it would fail a quality check but it does have 93K miles on it so?.I guess it should be worn out? Not all these hot spots are mine. I got her with 81K on the odometer.



Geez, sorry to hear and see this. It is just not getting any better. Last year Jim Jandik mentioned to me that he thought Bill Boudreau found a place to rebuild our DM flywheel. It might be worth checking unless you are considering other aftermarket options. I know I have an extra DM flywheel from my 90Z with 51K miles, but I don?t have access to it for a few months. Best wishes to get all resolved. [emoji1374]


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[1991 Corvette ZR-1]

Geez, sorry to hear and see this. It is just not getting any better. Last year Jim Jandik mentioned to me that he thought Bill Boudreau found a place to rebuild our DM flywheel. It might be worth checking unless you are considering other aftermarket options. I know I have an extra DM flywheel from my 90Z with 51K miles, but I don?t have access to it for a few months. Best wishes to get all resolved. [emoji1374]


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The plan is to install a 13 lb Fidanza I picked up for a good price new. I think I will appreciate the pep it adds to my ported top end, headers and 3.90 gears. Trying to squeeze every bit of performance I can out of what I have before one day doing a 368 or something similar. On top of the Redline Heavy Shockproof, I have an oversized countershaft shim from Bill B to install while the trans is out.

I figure between these two supplements, the gear rattle should be reduced quite a bit. I always read where people install the Fidanza and mention gear rattle but never read someone mention they shimmed the countershaft so we will see. It is a weekend pleasure only, so I do not mind extra chatter. I was not planning this anytime soon, but the grinding forced my hand early. At least it is cool weather for once.

[HAWAIIZR-1]

The plan is to install a 13 lb Fidanza I picked up for a good price new. I think I will appreciate the pep it adds to my ported top end, headers and 3.90 gears. Trying to squeeze every bit of performance I can out of what I have before one day doing a 368 or something similar. On top of the Redline Heavy Shockproof, I have an oversized countershaft shim from Bill B to install while the trans is out.



I figure between these two supplements, the gear rattle should be reduced quite a bit. I always read where people install the Fidanza and mention gear rattle but never read someone mention they shimmed the countershaft so we will see. It is a weekend pleasure only, so I do not mind extra chatter. I was not planning this anytime soon, but the grinding forced my hand early. At least it is cool weather for once.



Got it and understood. I did love the 13 lb Fidanza on my 90, but I had the SGC Stage 1 cams and could not stand the rattle. But I didn?t know about the oversized countershaft shim back then. I guess when I get to the point of needing a new clutch I may consider going Fidanza again, especially since stock cams in my 95. It?s sounds like you will be good to go. I?m curious to see how the shimmed countershaft works. [emoji1360]🤙🏼


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[1991 Corvette ZR-1]

Well, I am close to striking out on getting an OEM L98 plate. Feels like I am running out of options on the pull type clutch situation. I think I will check around a bit more but might have to return the flywheel and disc and possibly go to a RAM clutch kit setup. Which I absolutely hate the idea of. And it has nothing to do with loyalty to pull type, I just hate Teflon tape applications. I hate potential leak points that cannot be serviced unless I tear everything apart.

Major bummer!

[TX '90 ZR1]

I am not well versed in exactly which way you are wanting to go, but Jerry's has a large selection of items that might help you find what you are looking for.
Getting whatever from Jerry would assure the parts you purchase are compatible with the ZR-1 application.
:cheers:

[1991 Corvette ZR-1]

I am not well versed in exactly which way you are wanting to go, but Jerry's has a large selection of items that might help you find what you are looking for.
Getting whatever from Jerry would assure the parts you purchase are compatible with the ZR-1 application.
:cheers:

Thanks, Kenny. I already buy my share of parts from Jerry but did not see this particular item. The Valeo part even in L98/LT1 form seems to be tough to come by. Lots of ?Valeo? plate kits on eBay but no way to know it is an actual Valeo plate. Really want to make this work because I have all the parts minus the plate.

[richarde]

Regarding the fitment of an aluminum flywheel and the gear rattle at idle, I have an aluminum flywheel with a Carolina Clutch kit 04-114 Stage 2, Carolina Clutch shim kit C4SHIMKIT and am using Red Line Heavy Shockproof Gear Oil. The gear noise on idle is not an issue and is perfectly acceptable, being on a par with my other '90 which has a stock DM flywheel. I must admit to being a little nervous when first installing the aluminum flywheel due to all the stories of excessive noise on idle etc. However, I am really pleased that I fitted it now as throttle response is great! Also, the clutch pedal pressure with the Carolina Clutch is nice and light with no chatter on take off.

[1991 Corvette ZR-1]

Regarding the fitment of an aluminum flywheel and the gear rattle at idle, I have an aluminum flywheel with a Carolina Clutch kit 04-114 Stage 2, Carolina Clutch shim kit C4SHIMKIT and am using Red Line Heavy Shockproof Gear Oil. The gear noise on idle is not an issue and is perfectly acceptable, being on a par with my other '90 which has a stock DM flywheel. I must admit to being a little nervous when first installing the aluminum flywheel due to all the stories of excessive noise on idle etc. However, I am really pleased that I fitted it now as throttle response is great! Also, the clutch pedal pressure with the Carolina Clutch is nice and light with no chatter on take off.

Hi Richarde, glad you mentioned Carolina Clutch. I was looking around their site and considering just ordering a kit from them. I may give them a call and see if it is possible to just pay for a plate. Probably not, but could not hurt to ask. I think I am obsessing too much over OEM when most likely ALL of these off brand plates for the L98/LT1 are made by factory owned by Valeo. Some Google searching off the number on the plate I took off recently yielded some interesting results. It is not really a Valeo, but it is, if that makes any sense.

Edit: ordered the Carolina Clutch kit you referenced. It is what it is.

[richarde]

Hi - I hope that you'll be happy with it. As a comparison between the OEM clutch and DM flywheel in my Charcoal car and the aluminum flywheel and Carolina Clutch in my black car, the Carolina Clutch has a lighter clutch pedal with really good take off - no chatter. It grips fine with no evidence of slip. The C4 Shim Kit is certainly worth getting and fitting whist the gearbox is out.

[1991 Corvette ZR-1]

Well anyone got a bearing puller tool or tips they can recommend that is 100% effective? I got a slide hammer kit thinking I had a good kit and it is not gripping the inside of the old bearing shell too well. I was able to fish the guts out of the trashed bearing so it is just the shell now and it is IN there. Soaked it with WD40 but did not help much trying to slide hammer it out. Local autozone and advance have loaner kits but not right sized pieces get inside the bearing.

[Jagdpanzer]

A lot of us have had good results pulling pilot bearings with the Harbor Freight blind hole hammer puller sku 95987
https://www.harborfreight.com/blind-hole-bearing-puller-95987.html

Similar tool also available on Amazon.
https://www.amazon.com/KUNTEC-Puller-Internal-Bearing-Remover/dp/B08HWC84MF/ref=sr_1_17?adgrpid=1333708171504179&hvadid=83356831877274&hvbmt=be&hvdev=c&hvlocphy=66743&hvnetw=o&hvqmt=e&hvtargid=kwd-83357111619136%3Aloc-190&hydadcr=7514_10797916&keywords=blind+hole+bearing+puller&qid=1638154222&sr=8-17

[1991 Corvette ZR-1]

A lot of us have had good results pulling pilot bearings with the Harbor Freight blind hole hammer puller sku 95987
https://www.harborfreight.com/blind-hole-bearing-puller-95987.html

Similar tool also available on Amazon.
https://www.amazon.com/KUNTEC-Puller-Internal-Bearing-Remover/dp/B08HWC84MF/ref=sr_1_17?adgrpid=1333708171504179&hvadid=83356831877274&hvbmt=be&hvdev=c&hvlocphy=66743&hvnetw=o&hvqmt=e&hvtargid=kwd-83357111619136%3Aloc-190&hydadcr=7514_10797916&keywords=blind+hole+bearing+puller&qid=1638154222&sr=8-17


Phil, that second link is the exact one I have. The adapters do not appear to have enough tooth to hook onto the back of the bearing. I have slide hammered it a good amount but the fittings eventually pop out minus the bearing. I may try a few more times before looking at other options. I have seen some actual pullers that could be promising if I can find one that will fit inside the bearing. Then I could gently extract versus the slide.

I sent my flywheel and plate out to Marc for a balance and it will not arrive there until Thursday so I guess I have some time to mess with it.

[Shizap]

I used this pilot bearing puller I rented from autozone. I had to file the ends to give a more secure grip and it did the job nicely.

Best of luck,
Scott

[1991 Corvette ZR-1]

I got the bearing out, finally. I found an old can of PB Blaster and filled the crank end with it and let it sit for a few hours. Then it came out but not without a fight. My fears were confirmed that not even the cup plug made it untouched from the improper install and bearing failure. There is some damage but it does not look too bad. I have a fluted input bushing that I will be installing. I will never use a bearing if there is a suitable bushing available. How the bearing did not take out the input shaft tip I will never know.

[1991 Corvette ZR-1]

Any of you LT5 gurus know what this indicates? I love finding stuff like this. It was hidden behind a thick wall of clutch dust I cleaned off. Looks like a 3 with a line over it.

[WARP TEN]

Any of you LT5 gurus know what this indicates? I love finding stuff like this. It was hidden behind a thick wall of clutch dust I cleaned off. Looks like a 3 with a line over it.

Or "1m" as in 1mm? Personally, no clue. --Bob

[1991 Corvette ZR-1]

I installed the pilot bushing. Bill B loaned me a sweet driver / alignment tool, just a cut off ZF input shaft. And I came across something interesting. I was striving for a depth of 16mm to 17mm in from the end of the crank snout but I am right at 14mm in. The reason for this is the input shaft piece I am using for a driver will not proceed past this point.

The reduction of the inner circumference of the crank is for the bearing or bushing to snug up but too small for splined portion of the input shaft. This tells me at least the input shaft will never be this close in on the actual gearbox once everything is back together. Before it reached the face of the bearing it would be literally grinding the metal on the inside of the crank.

So I found an interesting comment made by Jerry from an old thread in 2017 that he would space both, pilot bushing, or pilot bearing, recessed 7/16" (0.437") from the end of the crank. At that location, the pilot bushing will engage the input shaft completely, providing maximum life of the bushing. Likewise, the bearing will work just as well at the same distance.

.437? works out to 11mm, thanks to a conversion calculator. As my bushing depth sits now, I am just a hair under 14mm when I checked with my Vernier caliper. I measured off the snout portion of the crank the flywheel mates to. Bill suggested 16mm, 17mm absolute maximum from flush. So, there is some wiggle room in there for depth. I do not want to push my luck with using a long socket on top and end up compromising the bushing. I think I am in a good spot with depth of the bushing. I taped off the input shaft and how far it would physically fit into the crank and the tape is a bit back compared to where the tape mark is on Jerry?s input shaft picture he provided.

[A26B]

.................... I taped off the input shaft and how far it would physically fit into the crank and the tape is a bit back compared to where the tape mark is on Jerry?s input shaft picture he provided.

That is how it should be. Your tape mark registers the interference point where the input shaft spline section bottoms out in the crankshaft. My tape mark registers the input shaft location as installed, transmission mounted to bellhousing. The difference is the clearance/set-back of transmission input shaft.

You are in good shape.

[1991 Corvette ZR-1]

Parts showed up from Marc and I made some progress if just putting on the flywheel can be called progress. Every little bit helps, but it is Florida and I was drenched after just torquing the flywheel down. It has been hotter than normal considering we just had a nice cold snap come through. Marc has been a tremendous help, as usual! I am not in a big rush to install everything, as the test drive afterwards will happen on the weekend with less cars on the road. I did find something interesting in the FSM.

It states Important - the flywheel must be installed with the crankshaft dowel pin in the 3 o clock position.

Mine just happen to be pointing to three as I installed the Fidanza, if that is what the FSM is referring to. Anyone know why the FSM states this? In the 1991 FSM, it is at top right of page 7C - 13.

[1991 Corvette ZR-1]

Little more progress. Used Marc?s shims under the plate. ZF Doc?s custom alignment tool made the installation a breeze to line up the parts. I forgot to mention that when I originally took the old parts off the car, the clutch fork, stud and throwout bearing were bone dry. So whoever put the new parts on did not lubricate anything. Which would explain why I was getting a squeaking noise from the clutch pack when I would use the pedal sometimes.

Clutch fork stud was surprisingly not gouged or worn down. I used Lucas Red N Tacky for the lubrication points on the clutch slave rod contact, clutch fork stud and fork to throwout bearing. To avoid any type of contamination of the fluted bronze bushing with grease when reinstalling the transmission, I will add the grease to the guide tube. That way there are no worries about the tip touching the inside of the throwout bearing and dragging grease into the bushing during install.

[1991 Corvette ZR-1]

Finally buttoned everything up and took her for a 5 mile test drive. Runs nice! Definitely more peppy now accelerating, but I didnt get past 4K rpm on this drive. 500 miles of stop and go traffic before I feel good about winding it out some. I dont pop clutches, but better safe than sorry. No flywheel noise! Not a peep. The heavy shockproof and ZF Docs thicker countershaft shim seem to have done the trick. At idle, it sounds just like it did with the dual mass wheel.

The launch from stop does not seem to be a problem so much as more rpms required when changing gears. I could take my time shifting with the dual mass, guess I will have to change that habit. I have 3.90 gears so that may be helping with the bogging issue from stop.

[We Gone]

That's great news

[1991 Corvette ZR-1]

Just wanted to do a quick follow up that I have about 300 miles of driving in so far on the new lightweight flywheel. Again, no noise at idle at all. None. It is like running the dual mass. I believe the MVP here is the thicker countershaft shim that I installed from ZF Doc. The redline heavy shockproof was a great assist. Trying to keep it stop and go and not just cruising. So far, everything has been great. Earlier today I did roll into it and let it go to 6K rpm and I can definitely feel the difference.

Before with the dual mass, I could shift without issue at about 2500 rpm. Now, I need to get it to about 3500 rpm, then be more swift with gear selection or rpms plummet. During the times I happen to be cruising, I enjoy 3000 to 3500 rpm area now where before I stayed around 2500 running the DM. I feel like this upgrade pairs very well with the 3.90 gears.

Ported top end, headers, Corsa full length, 3.90 gears and now the aluminum flywheel. I think that is about as quick as I can make her without getting into the heavy stuff.

[HAWAIIZR-1]

Just wanted to do a quick follow up that I have about 300 miles of driving in so far on the new lightweight flywheel. Again, no noise at idle at all. None. It is like running the dual mass. I believe the MVP here is the thicker countershaft shim that I installed from ZF Doc. The redline heavy shockproof was a great assist. Trying to keep it stop and go and not just cruising. So far, everything has been great. Earlier today I did roll into it and let it go to 6K rpm and I can definitely feel the difference.



Before with the dual mass, I could shift without issue at about 2500 rpm. Now, I need to get it to about 3500 rpm, then be more swift with gear selection or rpms plummet. During the times I happen to be cruising, I enjoy 3000 to 3500 rpm area now where before I stayed around 2500 running the DM. I feel like this upgrade pairs very well with the 3.90 gears.



Ported top end, headers, Corsa full length, 3.90 gears and now the aluminum flywheel. I think that is about as quick as I can make her without getting into the heavy stuff.



Congrats and great news! Thanks for sharing.


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