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Hi everyone my name is Anthony I'm new here..hope to make new friends..question,I have a chatter in my 6 speed manual ZF trans..96 grand sport lt4... Just replaced my clutch with a high performance ram clutch system complete w/ flywheel,thinking it was my bearing,but noise is still there...anyone knows if this chatter is normal for this ZF trans...only in neutral not through gear change....please let me know if anyone has this issue and what was the fix or its just normal...Thanks Anthony
Hi everyone my name is Anthony I'm new here..hope to make new friends..question,I have a chatter in my 6 speed manual ZF trans..96 grand sport lt4... Just replaced my clutch with a high performance ram clutch system complete w/ flywheel,thinking it was my bearing,but noise is still there...anyone knows if this chatter is normal for this ZF trans...only in neutral not through gear change....please let me know if anyone has this issue and what was the fix or its just normal...Thanks Anthony
Hi and welcome to the forum! This issue has been covered many times here if you do a search, but understand as you are new and would like to make friends; I surely would not mind befriending someone with such a fine C4! A 96 GS is at the top of the food chain with the ZR1'S, in the C4 world so good for you first off.
If you changed out the dual mass FW for a single mass aluminum (especially) or even the single mass FW in steel form, you will experience gear rattle from the ZF tranny; in EOM form, these trannys came with dual mass FW's to dampen the gear rattle, due to how they are cut from the factory. Dual mass FW's for these cars are practically extinct now, so finding a new one is nearly impossible. What you have is normal if that is what you have done.
If you changed out the dual mass FW for a single mass aluminum (especially) or even the single mass FW in steel form, you will experience gear rattle from the ZF tranny; in EOM form, these trannys came with dual mass FW's to dampen the gear rattle, due to how they are cut from the factory. Dual mass FW's for these cars are practically extinct now, so finding a new one is nearly impossible. What you have is normal if that is what you have done.
Very common issue when replacing the DM flywheel with a lighter flywheel.
The zf6 is very sensitive to to alignment. I had mine out twice trying to find the cause of the noise (sounded like a bad bearing) when in neutral with the clutch pedal released. Went away when I stepped on the clutch pedal. After several conversations with Bill at zf Doc I pulled it again and used a straight edge to check the mounting surfaces. There were some high spots. I used a large flat file to true up the surfaces. Problem solved. Go to zfdoc.com for info on these transmissions.
Very common issue when replacing the DM flywheel with a lighter flywheel.
Congrats on the LT4 and welcome.
Thank You it's good to be here....I'm getting very bad rattle while in neutral and while I'm driving,very bad...and as before 2nd gear hard to go in at time,have to get on the car a bit to engage to 2nd...but at slow speeds very hard...can't go on the highway,rattle is terrible....
The zf6 is very sensitive to to alignment. I had mine out twice trying to find the cause of the noise (sounded like a bad bearing) when in neutral with the clutch pedal released. Went away when I stepped on the clutch pedal. After several conversations with Bill at zf Doc I pulled it again and used a straight edge to check the mounting surfaces. There were some high spots. I used a large flat file to true up the surfaces. Problem solved. Go to zfdoc.com for info on these transmissions.
Will do thank you all for your help....it's just a pain to go through the removal again..
Thank You it's good to be here....I'm getting very bad rattle while in neutral and while I'm driving,very bad...and as before 2nd gear hard to go in at time,have to get on the car a bit to engage to 2nd...but at slow speeds very hard...can't go on the highway,rattle is terrible....
Does it only rattle when you are accelerating on the highway? but goes quiet when you let off the throttle?
Does this car still have the CAGS system connected? This is the 1 to 4 shift under such and such throttle, under some MPH.... basically when going really slow? If this is still connected on the trans it will force you to shift into 4th.
If this does not have CAGS hooked up, you may have some trans issues. Or driver shifting mod needs to be done. Does it have a short shifter on it at all?
Does it only rattle when you are accelerating on the highway? but goes quiet when you let off the throttle?
Does this car still have the CAGS system connected? This is the 1 to 4 shift under such and such throttle, under some MPH.... basically when going really slow? If this is still connected on the trans it will force you to shift into 4th.
If this does not have CAGS hooked up, you may have some trans issues. Or driver shifting mod needs to be done. Does it have a short shifter on it at all?
Hi it rattles when in neutral,and when given throttle to all gears on the highway steady,but when throttle is off it goes away....what is CAGS...I've noticed a connector dis-connected on trans ( white ) connector,is that the round cylinder looking piece...everyone is telling me that it could be the front output what bearing needs to be shimmed...very concerned about this noise....
If you changed out the dual mass FW for a single mass aluminum (especially) or even the single mass FW in steel form, you will experience gear rattle from the ZF tranny; in EOM form, these trannys came with dual mass FW's to dampen the gear rattle, due to how they are cut from the factory. Dual mass FW's for these cars are practically extinct now, so finding a new one is nearly impossible. What you have is normal if that is what you have done.
No. A steel billet wheel is a fine replacement. Even with your LT4. Even after you stroke it!
I have a brand new OE DMFW if you want to buy one. Brand new, in the box. It was probably the last one you could get. For $1K it's yours.
No. A steel billet wheel is a fine replacement. Even with your LT4. Even after you stroke it!
I have a brand new OE DMFW if you want to buy one. Brand new, in the box. It was probably the last one you could get. For $1K it's yours.
Yes.........if you want a steel replacement............
Rather have the aluminum personally, but thanks for your opinion!
Glad you enjoy it. There are folks who have gone with a steel one piece FW that have experienced gear rattle as well.
You can run the idle speed up a bit in the tune and have no or little rattle with an aluminum FW OR steel one piece.
Just posting to give another +1 - the rattling is normal with a lighter flywheel. I just picked up my LT4 from a forum member here about a month back and it has the same flywheel and rattling. I dropped it off at a local corvette shop last weekend for some unrelated work, and the owner confirmed that's totally normal with these lighter flywheels.
I'm sure if you swapped to a proper dual mass flywheel the sound would largely go away, but then you have a heavy flywheel and a lighter wallet :P Up to you.
Just posting to give another +1 - the rattling is normal with a lighter flywheel. I just picked up my LT4 from a forum member here about a month back and it has the same flywheel and rattling. I dropped it off at a local corvette shop last weekend for some unrelated work, and the owner confirmed that's totally normal with these lighter flywheels.
I'm sure if you swapped to a proper dual mass flywheel the sound would largely go away, but then you have a heavy flywheel and a lighter wallet :P Up to you.
Hi there,the reason for changing the clutch was that it was making the same noise with the dual mass flywheel..thinking it was a bad bearing...so I went with a high performance dual disc system with flywheel...makes the same noise,so I had it diagnosed yesterday and it came down as being a bad trans...
Hi it rattles when in neutral,and when given throttle to all gears on the highway steady,but when throttle is off it goes away....what is CAGS...I've noticed a connector dis-connected on trans ( white ) connector,is that the round cylinder looking piece...everyone is telling me that it could be the front output what bearing needs to be shimmed...very concerned about this noise....
Yes, that cylinder on the drivers side of the trans controls CAGS. Unplug it and CAGS is deactivated.
The ZF6 will make noise with a single mass no matter what you do. So now you have this other issues on top of what you had before.
the one thing with the single mass is that when you put the clutch pedal in, the noise should go away.
I drove and LT4 with an aluminum single mass flywheel. It made noise. At idle with the clutch out, and a slight growl under load.
My L98 with a steel single mass was so loud that I never even got it off the jack stands.
If you had the wrong trans fluid in the trans this whole time, I hope for you a simple change of fluid clears it all up.
If not, I would be wondering if the second gear synchro is shot now.
I know a lot of time has gone by, but I don't think many people are qualified to work on this trans. It is not some T-56 or Muncie 4 speed.
I am wondering who told you the trans is ruined?
The purpose of the dual mass, is to absorb the trans vibrations. the dual mass is just 2 parts of a flywheel that can be locked to each other but only allow 1/4 inch or rotation movement between the 2 surfaces. When the gears put out pulses, the flywheel is suppose to absorb them. Someone had a cutaway on here. Once you remove this this part of the process with installing a single mass, you will now have gear noise. It does not matter if the single mass is titanium, cement, carbon fiber or lead. It is going to make noise.
My understanding is the ZF6 has gears cut to make noise, and the earlier models are far worse then the later, like in your LT4.
My real life experiences supports this theory.
Thanks guys,I did speak to the zf doctor Bill I explained to him the situation with my trans,and he says that the trans could be wiped out...even with the original dual mass flywheel,it was making the same noise,thinking it was the clutch bearing..but when removed the clutch was bad and the bearing was too...I replaced the whole clutch system with a dual clutch system and a billet flywheel...metallic pads on disc and the bearing is my slave cylinder,push system works great,but noise is annoying...even with the right oil,it still makes noise...I'm ordering a trans soon from the zf doctor
06-20-2015, 09:52 AM
help with a chatter sound in my 6 speed manual
Very common issue when replacing the DM flywheel with a lighter flywheel. 
