I got my new clutch (LUK -Carolina Clutch stage II) and single mass steel flywheel put in, also a new Hurst shifter. All works great except there is a in the trans noise now that I never noticed or it got louder.(also installed quieter exhaust too) It only makes noise in neutral (the old "rock in a tumbler" sound, or when you first start off in first kind of a differnet noise. Push in the clutch or when cruising, nice and quiet.
It's like something is loose, I think it gets louder or fluctuates as you sit in idle in neutral.

My mechanic thinks it is the input shaft bearing going out. Does this sound like a bearing, or could it be the shifter and maybe the combination with the single mass flywheel? The shifter feels great and it very tight.

 

That's why GM used the dual mass flywheel on the ZF6.
Everyone that has changed to non stock flywheel has reported the "rock in a tumbler" sound. These transmissions make a lot more gear noise than others.

You can find lots of info at: http://www.zfdoc.com/

From their FAQ's:

(Q.) Bill, I own a 1990 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? Duane Barcena of north Chicago.

A.) Duane, 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.

 

Its just standard "clutch chatter".

ALL ZF6 mated with a single mass flywheel have it.

Been hating that sound for years. I think I will go back to dual mass the next time I need a new clutch/flywheel.

 

Well I have read about it before, but I never imagined it would be this loud, I thought it was just people with quiet cars and noticing a new noise. I would swear there was something wrong if others didn't say it was normal, even my mechanic thought it was a bearing.

I went to the single because Carolina Clutch said I needed a higher performance clutch and must convert to a single to do it. So everyone just lives with the noise? Why can't you use a dual with a hi-perf clutch? Why does the single make noise, it doesn't do this in other types of cars does it, specific to a ZF?

 

Some other transmissions do it to, but not many (the old muncie rock crushers were even worse). It's because of the relatively straight-cut gears in the trans.

I just live with the noise, but mine is also not a daily driver. The exhaust drowns it out for the most part.

Using a clutch disc with a sprung hub helps a little. Some have also had luck with synthetic trans fluid quieting it down a but, but that topic always results in a heated debate.

As far as not being able to run a performance clutch with a dual-mass, that's at least partial BS. There are a load of performance single-disc clutches available that use the standard flywheel and pressure plate. I have a Mcleod 500-series in mine (supposed to be good for 500hp). I'm using a single-mass FW, but it also bolts up directly to a stock DM flywheel.

When you really go nuts, then you move up to a dual-disc setup or a pure race setup. None of those will work with a stock DM flywheel.

 

i had the same setup with a fidanza aluminum single mass i purchased from carolina clutch.

i hated it with a passion from the word go, and it never got better for me.

my car is a daily driver, so i care.

it's one of the several reasons i had it ripped out in favor a new stock setup. it's one of those times that "stock" is better.

ps: i'm no ZF expert. but in my case, i am an expert at hating the ultra light single-mass flywheel.

 

Well I had a stock clutch in there, but only lasted less than 12K miles, throwout bearing was eaten up. CC said I needed a hi-po one for the power level I have now. I didn't go with the aluminum because I had heard they suck for a DD.

Good news is today, I didn't notice it as much, seemed queiter. Maybe because I felt relieved, had the radio on, and wasn't listening for it as much since I know it isn't going to explode! lol I think I can live with it, maybe even out some insulation around the center console.shifter area to help dampen the noise.

How much is the McLeod?

 

Mine rattles up to @ 2300rpm, then the noise goes away

 

ah the price for performance

 

I made the mistake last year of using a fidanza SMFW with a new clutch. The noise was so bad I switched back to a DMFW real quick. I have heard opinions both ways, and I think if yours is a DD you won't be able to stand it. The guys who don't use theirs as a DD don't seem to mind the extra noise much.

 

That's just how it is.
I was told before I had mine put in "This is going to make a lot of noise. Just so you know up front. Are you ok with this?"

"Sure" I said.

He said "I had one guy that we installed this for after telling him the same thing. He drove it home. Drove it back the next day and paid to have a whole new setup put in because he didn't like the noise"

"My car is already loud and I can't hear anything over the radio anyway" I replied back.

....

I got my car back and wow yeah, it chatters like mad.

BUT I am used to it. People ask me when I pull into car shows all the time "whats wrong with your car?".. I always have to explain why it's making that noise.

I have a Spec 3 clutch and flywheel in there now. So now it's hard to get off the line sometimes AND it chatters... it makes a lot of fun in the fast food drivethrough BOG CHATTER CHATTER CHATTER BOG CHATTER!!

 

I too have the Fidanza singlemass flywheel, along with a SPEC stage III+ clutch. It makes that noise.

My suggestions are:
1. Shut your car off at drive thrus. Sitting at a drive thru just wastes gas anyways.

2. Be in the right gear. You cant go lugging up hills in 5th anymore. My rattle is more pronounced if Im on the gas up a hill.

3. Dont be a pan$i and enjoy the noise. This isnt a VW bug convertible. Corvettes portray a tire-smoking performance image.

Maybe my setup is different? I hear people moan about the single-mass flywheel setup noise all the time. For me, its only loud when I want it to be loud (full acceleration low gear, high gear engine lugging, etc.).

Maybe my dual-mass was bad to begin with and bc of that I dont notice all that much extra noise? I dont know.

 

BUT I am used to it. People ask me when I pull into car shows all the time "whats wrong with your car?".. I always have to explain why it's making that noise.

I have a Spec 3 clutch and flywheel in there now. So now it's hard to get off the line sometimes AND it chatters... it makes a lot of fun in the fast food drivethrough BOG CHATTER CHATTER CHATTER BOG CHATTER!![/QUOTE]


Yeah, that is what I hate, it sounds like a POS sometimes at idle, and I already explain to passengers before they even comment! lol
It's not so bad most of the time, no that I know it is the norm with these SMF. Seems worse on an incline,and of course the lower the RPM the worse it sounds and if cold. If Idon't think about it with the radio on, I hardly notice now. It is kind of embarrasing in parking lots and lights, I push in the clutch and turn it off fast! lol

 

Yup - same experience here .

I had one guy telling me it was a rod knock, another guy told me I need to adjust my valves because they were making noise . FWIW, my injectors are loud too, so if and when something IS actually wrong, I'll never know!

My car isn't a DD, but I'm ready to quiet it down. If a DMFW can handle an occasional trip to the drag strip, I might consider going that route.

 

You can try raising your idle speed to get rid of some of the sound. But just push in the clutch. It's no big deal.

 

Yep, not a big deal now, but would rather it not be there of course.
My idle is about 900, don't want it any higher.

Speaking of holding in the clutch. I learned to drive a manual, and that is what I have always had. My Dad told me then, to never hold in the clutch when stoped, it wears it out faster.
Is this true?

 

Jeffvette just noticed your quote!
Dooooooooooong!!! What's-a-happen'n hastuff?! lol

 

LOL seems that deal worked out fairly well for me as well.

 

indeed, and i'm glad for both of us