Dual Mass Flywheel Problem?

[97vette]

Hello everyone,

I'm having some trouble with an 89 corvette with the ZF 6 speed and I'm hoping that some of you might be able to help me. I just recently changed the clutch, master and slave cylinder on the car. It seemed to run great. However, after a few days, there seemed to be a sound coming from below like rocks in a can or a diesel motor on a truck. Since this corvette is low mileage (~35,000 miles) and the flywheel looked alright visually when the clutch was out, I figured that either 1) the clutch was wrong for the car, or 2) the clutch was not installed properly. So, since I'm a glutton for punishment, I decided to take the whole thing apart and try a different clutch brand. I was absolutely meticulous in my re-installation. Frustratingly enough, the problem is still there with this new clutch. This fact would lead me to believe that the "rocks in a can" sound is possibly coming from the two discs chattering on the dual mass flywheel.

I did indeed read the FAQ on www.ZFdoc.com. One of the questions seemed relevant to my problem--except for two differences between my problem and the one diagnosed on zfdoc: 1) my "rocks-in-a-can" sound only occurs when the vehicle is hot and has been driven for a little distance (~ 20 miles each time) and, more importantly, 2) the sound does not go away when the clutch pedal is pushed to the floor.

Has anyone had a similar problem? Is it possible that the new clutch put more of a stress on the flywheel and that the rubber between the two discs on the dual mass was thus compromised? If so, does anyone know where I can find a new dual mass flywheel? (I wouldn't necessarily mind converting to the single mass solid steel flywheel, but I'm worried about the potential for some weird transmission noises, which was the very thing I was trying to avoid in replacing the clutch/throwout bearing/pilot bearing.)

Any help you guys could give would be greatly appreciated! Thanks!

Joshua

 

[Hib Halverson]

Cars with ZFs can make "two versions" of that noise.

The first is the normal gear rattle from the early version of the ZF S6-40. Gear rattle gets worse if the idle is rough or unstable. It can be reduced but not eliminated by changing lubricant to Red Line Light Shockproof and taking measures to improve idle stability. In your case, since you say the noise gets louder at the trans warms up, I think some of your problem is the trans itself. I'd change the lube to Red Line Light Shockproof and see what happens.

The second is indicative of a failed dual mass flywheel. The early versions of that part were more prone to failure than were the later ones and, since you have an 89, you've got the worst of the bunch. A characteristic of a failed dual mass is a rattling from the flywheel, right after you turn off the key, as the engine comes to a stop.

The two noises can combine to make quite a rattle.

You can convert to a standard flywheel....the McLeod aluminum wheel is the best IMO.... but gear rattle from the trans will be worse with a standard wheel.

 

[G Winter]

My 90 had the rocks in a can sound when it was warmed up. Mostly noticed it when I drove it in the garage where the sound bounced off the walls. It was worse with the clutch engaged but still did it disengaged . Eventually my clutch went out and I replaced both flywheel and clutch disk with OEM parts from Carolina Clutch and Performance, Inc.: Performance Clutches &amp Flywheels . Before I did this I called them to ask a few questions. They were very helpfull.
I was told that the flywheels wear out in as little as 40k miles. And by 90 don't even consider not replacing it.
After replacing clutch and flywheel the noise is gone totally.
mho is that your flywheel is causing the noise,most of which is actually coming from the transmission.
The price was very competitive.

Glenn

 

[97vette]

First of all, thank you very much for your advice! I used two different fluids the two separate times I changed the clutch. The first time, I used GM Synchromesh fluid. The second time, I used Castrol 10w60 synthetic oil. ( I couldn't find the recommended fluid either in the car's manual or on the side of the bell housing itself. The synchromesh was suggested by the Chevy dealer; the 10w60 by a local Corvette guru). How much of a difference can this fluid make that you had mentioned?

As for the idle, it seems to me to be a little bit low. It wavers between 6 and 700 rpms. However, there are no problems with stalling or anything like that. Also, if you put the engine under a slight load (e.g., ac turned on), the clacking sound seems to be less pronounced. Is it possible that a slight miss could make a clacking sound in the bell housing and that the recent clutch replacement could have been simply a coincidence that's leading me in the wrong direction?

 

[97vette]

Thanks for the help, Glenn.

I'm assuming that you were able to purchase a new dual mass flywheel from Carolina Clutch? I've been calling around trying to find a dual mass flywheel, but everyone seems to have discontinued them, including Carolina Clutch (whose supplier was LUK clutches). I would be rather hesitant to buy a used one, even one with low miles on it, considering that the flywheel in this car only had about 35K miles on it.

Considering the unavailability of the dual mass flywheels, should I have to replace the flywheel, it looks like my best bet is to go with a single mass solid steel flywheel and clutch kit from Carolina Clutch. Does anyone have this set up? How much louder is it with that than with the stock, dual mass flywheel? Does it sound like rocks in a can, like I'm hearing now, or is it just more gear whine?

Thanks!

Joshua

 

[G Winter]

The supply of the dual mass must have disappeared rather quickly , it was only about 10 months ago that I replaced mine. And yes I purchased it from Carolina Clutches.
If in fact they have been discontinued that is a bit disturbing if you want to keep the six speed quiet.

Glenn

 

[Itshakes]

DMF

Joshua- The Dual mass Flywheel is still available from your GM dealer. I just purchased one here in Illinois. It came from a warehouse in Ohio. The flywheel (LUK) was made in Brazil. The part # is 10174482. It is expensive--$1100. I think it's worth it. My car drives like new. You can get a clutch kit from Autozone, they are made by Valeo the OEM supplier. Don't forget to replace the pilot bearing!

 

[G Winter]

Last summer I bought the OEM flywheel from carolina clutch for just under $700 and a complete OEM clutch kit with bearings for just under $300 . Total bill on my front step was about $1027.00

Glenn

 

[97vette]

Glenn,

I've been on the phone with Carolina Clutch 3 times over the last couple of days. The sad truth seems to be that the dual mass flywheel has been discontinued as of now. GM claims that they can get one for me for about $1100. They told me that there were only 6 dealers left in the United States with the dual mass flywheel available. (If that's true, I'd buy them while you can!) While I'd be willing to pay 700, 1100 sounds a bit steep. GM claims that their supplier may start remaking the flywheel in August of this year, but I'd like to get the car back together before then.

Joshua

 

[G Winter]

Maybe the flywheel is a casualty of the manufacturing downturn. Suppliers having to shut down operations do to lack of work, so the flywheel isn't being built right along with everything else.
I think it was Hib that said last summer he saw someone resurface them. That still don't fix wear inside the flywheel.I did not throw my old one out for scrap, I think someone will figure out how to rebuild them.

Glenn

 

[LT4man]

The second time, I used Castrol 10w60 synthetic oil. ( I couldn't find the recommended fluid either in the car's manual or on the side of the bell housing itself. The synchromesh was suggested by the Chevy dealer; the 10w60 by a local Corvette guru). How much of a difference can this fluid make that you had mentioned?

With my experience and what I have found from talking to other Vette techs, the Castrol oil is the best that can be used. Hib is happy with the Red Line product line so that would also be a good choice. Since you have the Castrol already installed, I would stop there.

As for the idle, it seems to me to be a little bit low. It wavers between 6 and 700 rpms. However, there are no problems with stalling or anything like that. Also, if you put the engine under a slight load (e.g., ac turned on), the clacking sound seems to be less pronounced. Is it possible that a slight miss could make a clacking sound in the bell housing and that the recent clutch replacement could have been simply a coincidence that's leading me in the wrong direction?

Your idea about your idle is spot on! Congratulations on being so aware of a small detail.

The Dual Mass Flywheel was designed specifically to eliminate the harsh vibrations associated with a diesel engine. They worked so well in that application, that they were installed into high HP sports car engines.

I would very carefully check any and all symptoms relating to an engine miss.

Run codes. None? Good!

Inspect ignition wires for any traces of arcing.

Be sure spark plugs are all firing correctly.

Check for any type of vacuum leak.

Hope this helps.

AFTER REPAIRING YOUR VETTE, BE SURE TO SAVE THE !

 

[anniegreensprings]

flywheel weights

Joshua- The Dual mass Flywheel is still available from your GM dealer. I just purchased one here in Illinois. It came from a warehouse in Ohio. The flywheel (LUK) was made in Brazil. The part # is 10174482. It is expensive--$1100. I think it's worth it. My car drives like new. You can get a clutch kit from Autozone, they are made by Valeo the OEM supplier. Don't forget to replace the pilot bearing!

when you replaced your flywheel with an original one from GM, did you have to repalce any weights in it or did you just have to bolt it on? i need to know this as i'm in the process of replacing mine and i'm hearing different stories. thank you for your time.

 

[Itshakes]

Dual Mass Flywheel

I was lucky, as the the old flywheel had no weights on it. The holes that were drilled for balance were the same on the new one as on the old one. Take your old flywheel, and your new one to the machine shop and have the new one balanced the same as the old one. I put a new "roller" pilot bearing in also.

 

[vetteoz]

I was lucky, as the the old flywheel had no weights on it.

The stock DM flywheel has a weight cast into it on the engine side to suit the ext balance used on the 1 pce seal engines.
The smaller weights are supplied so it can be fine tuned to the exact balance of the original.

 

[Rex S]

Just put a Fidanza in it and forget about it for several years. Fidanza Flywheel & Performance Parts worked great in our 90Z.

 

[Hib Halverson]

Another good flywheel choice is McLeod.

Back in 1997, I put a McLeod flywheel, clutch and disc in my 95 and they've been trouble-free ever since.

Also, reading other posts above, there is confusion about why a dual mass flywheel is used. It is not to damp vibrations. That is addressed by the powertrain mounts, crankshaft damper and engine balancing.

Dual mass flywheels exist, both on medium- and heavy-duty trucks (regardless of engine type) and on Corvettes to damp or quiet transmission gear rattle. When prototype ZF S6-40s were first tested in vehicles, the gear rattle was unacceptable. GM adopted a dual-mass wheel as the solution. The reason the ZF has a problem with gear rattle is its unusually large (for a passenger car transmission) center distance and its massive gears. Combine a large center distance and big gears and you get gear rattle.

 

[LT4man]

Also, reading other posts above, there is confusion about why a dual mass flywheel is used. It is not to damp vibrations. That is addressed by the powertrain mounts, crankshaft damper and engine balancing.

Dual mass flywheels exist, both on medium- and heavy-duty trucks (regardless of engine type) and on Corvettes to damp or quiet transmission gear rattle.

According to the Patent information filed with the United States Patent Office:

Patent application title: [SIZE=+1]Dual-mass flywheel[/SIZE]

Inventors: [SIZE=+1] Hartmut Mende[/SIZE] [SIZE=+1] Bin Zhou[/SIZE] [SIZE=+1] Reiner Kistner[/SIZE]
Agents: [SIZE=+1] ALFRED J MANGELS[/SIZE]
Assignees: [SIZE=+1] LuK Lamellen und Kupplungsbau Beteiligungs KG[/SIZE]
Origin: [SIZE=+1]CINCINNATI, OH US[/SIZE]
IPC8 Class: [SIZE=+1]AF16F15121FI[/SIZE]
USPC Class: [SIZE=+1] 464 681[/SIZE]

Read more: Dual-mass flywheel - Patent application - including a primary mass that can be connected to the drive shaft of an internal combustion engine


​

[0003]Such torque transfer devices provided as dual-mass flywheels have typically proved useful in automobiles from medium size up, in particular in connection with diesel engines. In smaller vehicles, however, these devices have not become widely popular yet, in spite of their advantages, due to the comparatively high cost.

Read more: Dual-mass flywheel - Patent application - including a primary mass that can be connected to the drive shaft of an internal combustion engine

To learn all of the technology behind these unusual flywheels, please read the entire patent document. Quite lengthy, but very accurate.


​

 

[Hib Halverson]

IMO, that patent information is irrelevant to this discussion.

My statements as to why GM used a dual-mass wheel with ZFs is based on first-hand information. It came from both GM Powertrain and ZF in interviews I did in 1989-1991 period with Bill Zabritski, who was the Senior Engineer at GM for Manual Transmissions and ran the ZF development, and Engineers from ZF Industries. All these interviews were done in and around the Detroit area in that time frame for several articles I wrote back then on the ZF S6-40. These articles were published in Vette Magazine, Corvette Quarterly, Chevy High-Performance, and elsewhere.

While it is true that dual-mass wheels, especially those used in heavy-duty applications, can address engine vibrations, the reason GM used it on Corvette was to solve the problem with gear rattle.

The dual mass wheel in a Corvette has no practical role in damping engine vibration.

When C5 was introduced in 1997, the T56 had far less of a problem with gear rattle, both because it had a smaller center distance and smaller gears and because it was located in the rear of the vehicle.

Consequently, the dual-mass wheel was not necessary and was dropped from production...thankfully. If the dual-mass was necessary to damp engine vibration GM would have used it on C5.

 

[LT4man]

Also, reading other posts above, there is confusion about why a dual mass flywheel is used. It is not to damp vibrations. That is addressed by the powertrain mounts, crankshaft damper and engine balancing.

In my post #11 above, I was commenting why the dual mass flywheel was used in any automotive application.

In the interest of bringing additional knowledge to this site, I commented on why a dual mass flywheel was designed and built (outside of the use on Corvette).

Dual mass flywheels exist, both on medium- and heavy-duty trucks (regardless of engine type).

In my post #17, I was showing documentation of the beginnings of the dual mass flywheel. While it is now true these flywheels are being used in both gasoline & diesel engine applications, the flywheels were first designed to work specifically with diesel engines.

IMO, that patent information is irrelevant to this discussion.

I believe any information in a thread can be deemed relevant or irrelevant by the individual person reading the thread. In my world, I endeavor to understand the poster's reasons of posting a response and avoid commenting in writing on their state of mind.

It is not to damp vibrations. That is addressed by the powertrain mounts, crankshaft damper and engine balancing.

As far as the L98 and LT5 engine, the above statement is correct.

In the case of the LT1 and LT4 engine, the dual mass flywheel is used to quiet gear rattle and to balance the reciprocating engine mass.

On the LT1 and LT4 engine, the crankshaft is not balanced. The engine is not internally balanced. That job is left up to the flywheel and crankshaft damper. When one replaces a dual mass flywheel behind an LT1 or LT4 engine, the replacement dual mass flywheel must be balanced identically to the flywheel being replaced. If this is not done, vibration will inevitably harm the powertrain assembly.

Hope this clears up any misunderstanding regarding this marvel of automotive technology!

 

[vetteoz]

On the LT1 and LT4 engine, the crankshaft is not balanced. The engine is not internally balanced.

The rotating assembly on all 1 piece seal engines is externally balanced at rear and neutral at front including late L98's and Vortecs.