hello,

i got a 1993 c4 lt-1 manual zf black tag 117k miles.

the clutch is slipping when stepping on the gas pedal, especially in higher gears. motor just goes to high rpm but no power on the wheels.


would you change the clutch to a conversion kit incl. a simple 100 usd single mass solid flyhweel or just buy a new clutch disc and use the original dual mass flyhweel (slightly rattling in low rpm, but simple new flywheel will rattle, too maybe)?

i really want it to be silent. but performance is a bit more important to me.

how would a solid cheap flywheel perform compared to the original dual mass ? what's the difference there ?


a friend just replaced his clutch on his 95 and got massive rattling and noise now, that's what i wanted to avoid. some say a new simple and not so heavy flywheel will probably make noises too, that's why i have my thoughts of keeping the original dual mass flywheel?


for the parts, would you go with ecklers parts:

clutch: http://www.ecklerscorvette.com/corve...1989-1993.html

flywheel: http://www.ecklerscorvette.com/corve...4-1989-96.html


or with rockauto parts (550 euro instead of 850 euro to germany):

clutch: http://www.rockauto.com/catalog/more...nid=507&jpid=0

flyhweel: http://www.rockauto.com/catalog/more...nid=508&jpid=0


the ecklers parts "look" better and description says noise dampening, i don't care about the 300 euro more if it lasts long and is silent.

i guess the performance would be the same between ecklers and rockauto parts ?

would you recommend to replace the release bearing also at 117k miles or is this not really important (would cost me another 400 euro) ?

 

do it once, buy quality parts.

 

I would be extremely surprised if Ecklers had the DM flywheel in stock. Yes, I see that is says "In Stock" on that web page, but I've noticed from others' experiences that it's their MO to say they have something in stock when they don't and won't.

Any solid flywheel will likely make noise. No flywheel is going to make a profound difference in "performance", so I wouldn't buy a noisy flywheel just for the sake of "performance".

 

Yes, replace the clutch release bearing (AKA throw-out bearing), as well as replace the pilot bearing.

 

SPEC has an "Extra Mass" option on their steel flywheels (PN SC05S) to help keep the ZF quiet. That and a Stage 1 Clutch/TB/PP assembly (PN SC421Z) will do a good job on your 93.

http://www.specclutch.com/cars/Chevy...te/1993/Single

Will

 

I have the spec standard solid steel flywheel, and an lt4 hot can plus 1.6 rockers....no noticeable rattle. with a real aggressive cam, I hated the rattle. Shouldn't be a problem with stock to mild cam, or with the heavier flywheel as suggested.

I got it all from Carolina clutch a couple of years ago. Flywheel plus a clutch kit.

BUT... if your flywheel is ok, no reason not to use it either. F.Y.I. They say if it has less than 1/4" of travel it is ok.

 

I would change to a single mass, and a push type clutch. To change to a push type clutch you would need a hydraulic throwout bearing. The clutch parts I used before the engine swap were for an 88 C4 clutch kit and flywheel from NAPA. I don't have a part number for the throwout bearing.

I don't know what causes the transmission to rattle with some clutches. My guess would be the balance of the clutch. I say clutches not flywheels because when I converted to a single mass flywheel I used the same fly wheel with 3 different clutch kits (more later) and the transmission only rattled with one of them. Now I have a different engine, single mass flywheel, clutch kit, still no rattle.

The reason for 3 clutches was that when installing the first two I screwed up with a line for the hydraulic throwout bearing, and that did them in. The first one caused a rattle, but it has not rattled after that.

 

When i have replaced my clutch i have bought the OEM Clutch Kit at below address

[url]http://www.clutchcityonline.com

 

The rattle is the front bearing in the transmission, not the flywheel. The flywheel is Dual Mass so it can dampen the vibration/harmonics to the transmission and be quiet.

Lots of info from the ZF-Doctor

http://www.zfdoc.com/index.htm

Here's an exerp:
(Q.) Bill, I own a 1991 Corvette with the 6 speed ZF. I have a transmission noise which many other Corvette & Camaro owners report as "normal". This noise is most prominent in neutral & 1st gear and is commonly described as the "rocks in a can" sound. Two local companies that rebuild (only) Muncie & Borg-Warner 4 speeds have heard this description and believe it to be the front bearing and possibly one of the ball bearings rolling around inside the trans case. From your experience is this "really" the problem which many people report hearing only in THIS model trans? Dean of north Chicago.

A.) Dean, it would be a nearly impossible for a ball bearing to fall out of the main bearing case. If the noise goes away when you push the clutch in at idle,... that could be 1 of 3 things, either a bad dual-mass flywheel, or the flywheel is not an original dual-mass type but instead is a single mass type. The ladder situation will produce a sound known as gear clatter while in neutral which is harmless to the transmission. The springs in the clutch disc, which are not present in the disc of a dual-mass set up, will oftentimes produce a rattle like resonance in the 1K - 2K RPM range when under moderate to heavy power load settings. These are the drawbacks of converting over to a single-mass flywheel.
A bad input bearing in the transmission will normally produce a whirling or whining sound proportional in pitch to engine revs. In 1st gear the whine is most prominent decreasing in intensity in each subsequent gear to the quietest level being 4th gear (direct drive energy flow).
A bad dual-mass flywheel with a failing damper will sound like a diesel truck engine at idle or a clacking noise. Under certain load settings, this sound may be heard occasionally in 1st gear too.
The main bearings in a ZF S6-40 are very different from those used in Muncie & Borg-Warner 4 speeds. The ZF main bearings are self-contained non-preload non-tapered double-row type bearings. One row is comprised of cylindrical type bearings and the other row is comprised of ball type bearings. This type of bearing would be more similar to the type of bearings used in turbine engines.
If it sounds like a diesel engine at idle, the flywheel dual mass damper may be failing. What I've seen happen before is that when a flywheel is determined to be bad, some people choose to replace it with a less expensive single mass type flywheel where they can buy the flywheel, pressure plate with throw-out bearing and clutch disc for $800 instead of $750 for OEM flywheel and $300 for the clutch kit.
If it is more of a whining or whirling sound, the input bearing has been compromised. This results from the alignment of the transmission during reinstallation is off slightly where the trans, bell housing butt up to the block. I've never heard of a ZF S6-40 main bearing going bad on it's own. FYI, I've rebuilt 125 of these units and have at least 7K hours of experience with the ZF S6-40 design.

Hope this helps.

 

The rattle is not from the front bearing in the transmission! The size of the gears, the way that they are cut, and their overall layout and spacing result in what's call gear clatter. The dual mass flywheel dampened out the variations in load at idle that are experienced by the transmission. When your DM flywheel fails, or you replace it with a common SM unit you loose that ability and now those forces are transmitted into the transmission. A sprung hub will help, setting bearing clearances will also help but none of these will totally eliminate the noise. It is not detrimental to the life of the unit so it just comes down to user preference. Just my .02

 

Except its not the bearing, and the information you copied here from http://www.zfdoc.com/faq.htm also says this.

Its not the flywheel either, but currently I cant prove this.


The 1st single mass flywheel had 3 different clutches. If it was the flywheel all 3 clutches with the same flywheel would have had the rattle instead 1 out of 3 clutches.

The 2nd single mass flywheel and a 4th clutch the transmission has not rattle.

I don't believe it is caused by a single mass flywheel, but I may have a freak trans. I have had 2 single mass flywheels and 3 clutches cause no transmission noise.

 

Thanks for clearing that up! .....It dampens the noise from the transmission so you don't hear it. So if you go to a solid mass flywheel, there are some transmissions that will make more and some less that will make noise (from what I've read).

Make your best informed decision and choose wisely. There are also occasionally good use ones for sale, so be patient and you might just score a deal.

 

No. The DM flywheel dampens the power pulses going into the trans, so that the trans gears never rattle in the first place. If the trans gears rattle, you'll hear it no matter what kind of FW you have. The DM FW prevents the rattle from happening. A heavy single mass attempts to do the same thing.

 

The dual mass flywheel is more heavier and with the dual mass is better for to absorb the rotation engine vibration who make gearbox noise and the OEM clutch disc is without springs.
Instead we install a solid flywheel we need to have the clutch disc with springs for to absorb the rotation noise