ZF six speed problem
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ZF six speed problem
The zf trans in my 96 sounds like crap, it makes a very loud buzzing sound when accelerating in all six gears. Anything other than ultra light acceleration brings on the noise. Its also very noisy when idling in neutral. I've been in other zf equipped vettes and they didnt make the noises that this one makes, there is definitely something wrong. All the gears work and it shifts smoothly but it sounds like it's coming apart inside. What is causing the noise in the trans?
Drifting
Joined: Apr 2014
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From: Hawthorne CA
The zf trans in my 96 sounds like crap, it makes a very loud buzzing sound when accelerating in all six gears. Anything other than ultra light acceleration brings on the noise. Its also very noisy when idling in neutral. I've been in other zf equipped vettes and they didnt make the noises that this one makes, there is definitely something wrong. All the gears work and it shifts smoothly but it sounds like it's coming apart inside. What is causing the noise in the trans?
Zen Vet Master Level VII
Joined: Mar 2016
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From: Southlake, TX
When was the last time that there was a "legit" lube change in the gear box? Shifting smoothly, but noisy is typically a symptom of a mechanically sound trans with out the "cushion" effect that lubrication provided.
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I have no idea, I've only owned the car for a couple of weeks so far. You should hear this thing, it sounds like there is no lube in it at all. There are no traces of leaks on the outside of the trans so I'm assuming that it does have lube in it but I have no idea what kind of lube is in it. I know that using the wrong lube can make it have some noise but it's hard to believe that even the wrong lube can make it as noisy as it is.
Race Director
Joined: Sep 2001
Posts: 14,676
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From: NEwhere Ohio
The noise is from the countershaft rattling back and forth in its bore.
the real solution is to put in a slightly thicker countershaft shim. Zfdoc used to sell these .
you gotta pull the trans to do it, but once out its simple procedure.
if the noise
is real loud, its possible the previous owner did a clutch change and got rid of the factory dual mass flywheel (which is a heavy POS Band aid fix) / and did not put in a sprung hub clutch which is required when getting rid of the dual mass flywheel.
people will tell you that you have to have this dual mass flywheel to dampen noise but thats not true if you use a sprung hub clutch .
Again the noise comes from the countershaft rattling and putting a slightly thicker shim in there will get rid of 90% of the noise.
as for lube, dont dare use castrol 10w-60 bmw motor oil like some (including zfdoc’s outdated website) say.
gm syncromesh or amsoil syncromesh is what you want
the real solution is to put in a slightly thicker countershaft shim. Zfdoc used to sell these .
you gotta pull the trans to do it, but once out its simple procedure.
if the noise
is real loud, its possible the previous owner did a clutch change and got rid of the factory dual mass flywheel (which is a heavy POS Band aid fix) / and did not put in a sprung hub clutch which is required when getting rid of the dual mass flywheel.
people will tell you that you have to have this dual mass flywheel to dampen noise but thats not true if you use a sprung hub clutch .
Again the noise comes from the countershaft rattling and putting a slightly thicker shim in there will get rid of 90% of the noise.
as for lube, dont dare use castrol 10w-60 bmw motor oil like some (including zfdoc’s outdated website) say.
gm syncromesh or amsoil syncromesh is what you want
Last edited by dizwiz24; Jun 21, 2018 at 04:04 PM.
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Joined: Apr 2016
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The noise is from the countershaft rattling back and forth in its bore.
the real solution is to put in a slightly thicker countershaft shim. Zfdoc used to sell these .
you gotta pull the trans to do it, but once out its simple procedure.
if the noise
is real loud, its possible the previous owner did a clutch change and got rid of the factory dual mass flywheel (which is a heavy POS Band aid fix) / and did not put in a sprung hub clutch which is required when getting rid of the dual mass flywheel.
people will tell you that you have to have this dual mass flywheel to dampen noise but thats not true if you use a sprung hub clutch .
Again the noise comes from the countershaft rattling and putting a slightly thicker shim in there will get rid of 90% of the noise.
as for lube, dont dare use castrol 10w-60 bmw motor oil like some (including zfdoc’s outdated website) say.
gm syncromesh or amsoil syncromesh is what you want
the real solution is to put in a slightly thicker countershaft shim. Zfdoc used to sell these .
you gotta pull the trans to do it, but once out its simple procedure.
if the noise
is real loud, its possible the previous owner did a clutch change and got rid of the factory dual mass flywheel (which is a heavy POS Band aid fix) / and did not put in a sprung hub clutch which is required when getting rid of the dual mass flywheel.
people will tell you that you have to have this dual mass flywheel to dampen noise but thats not true if you use a sprung hub clutch .
Again the noise comes from the countershaft rattling and putting a slightly thicker shim in there will get rid of 90% of the noise.
as for lube, dont dare use castrol 10w-60 bmw motor oil like some (including zfdoc’s outdated website) say.
gm syncromesh or amsoil syncromesh is what you want
Race Director
Joined: Sep 2001
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From: NEwhere Ohio
I looked up the carolina stage 2 clutch and it does appear to be sprung hub.
the lightweight flywheel can be noisy and difficult to manipulate in stop and go traffic (easy to stall), but it is what i have in my 93 for performance reasons.
It weighs 12 lbs where the stock dual mass weighs 38 lbs.
some people put in a heavier (but still lighter than dual mass) 24 lb flywheel .
I cant answer whether a heavier (but still single mass ) flywheel will dampen trans noise.
The shimming is your best option IMHO. Btw you need to get calipers and measure your current shim thickness. Zfdoc adds a few thousandths of an inch and gets you a thicker one. You have got to contact him for instructions.
also the shimming will eliminate 90% of the noise and not 100 %.
This is not an issue specific to zf6 either. My mustang buddies do the same on theirs to reduce rattle.
the lightweight flywheel can be noisy and difficult to manipulate in stop and go traffic (easy to stall), but it is what i have in my 93 for performance reasons.
It weighs 12 lbs where the stock dual mass weighs 38 lbs.
some people put in a heavier (but still lighter than dual mass) 24 lb flywheel .
I cant answer whether a heavier (but still single mass ) flywheel will dampen trans noise.
The shimming is your best option IMHO. Btw you need to get calipers and measure your current shim thickness. Zfdoc adds a few thousandths of an inch and gets you a thicker one. You have got to contact him for instructions.
also the shimming will eliminate 90% of the noise and not 100 %.
This is not an issue specific to zf6 either. My mustang buddies do the same on theirs to reduce rattle.
Last edited by dizwiz24; Jun 21, 2018 at 10:48 PM.
Melting Slicks
Joined: Apr 2007
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Even with a sprung hub disk, with an aluminum FW, you will still get rattle from the ZF. I know because I run the same exact set up but have a sprung hub disk. I set m idle speed up to 1,000 RPM which greatly reduced the noise at idle with the clutch disengaged. If you step on the clutch all the way down and the noise goes away, that is the issue. My car with the bigger cam doesn't sound bad at 1,000 RPM and actually idles smooth there.
Or like dizwiz states you can contact ZF doc. and have shims made for the counter shaft. That requires pulling the tranny of course. The noise is fine however other than possibly annoying.
Did you not hear the gear rattle before you purchased it??
Or like dizwiz states you can contact ZF doc. and have shims made for the counter shaft. That requires pulling the tranny of course. The noise is fine however other than possibly annoying.
Did you not hear the gear rattle before you purchased it??
Last edited by 856SPEED; Jun 21, 2018 at 11:46 PM.
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Even with a sprung hub disk, with an aluminum FW, you will still get rattle from the ZF. I know because I run the same exact set up but have a sprung hub disk. I set m idle speed up to 1,000 RPM which greatly reduced the noise at idle with the clutch disengaged. If you step on the clutch all the way down and the noise goes away, that is the issue. My car with the bigger cam doesn't sound bad at 1,000 RPM and actually idles smooth there.
Or like dizwiz states you can contact ZF doc. and have shims made for the counter shaft. That requires pulling the tranny of course. The noise is fine however other than possibly annoying.
Did you not hear the gear rattle before you purchased it??
Or like dizwiz states you can contact ZF doc. and have shims made for the counter shaft. That requires pulling the tranny of course. The noise is fine however other than possibly annoying.
Did you not hear the gear rattle before you purchased it??
Last edited by TheGreek!; Jun 22, 2018 at 12:08 AM.
Team Owner
Joined: Sep 2003
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Yes, I heard the rattle before I bought it but it seems louder now, probably because I'm paying more attention to it. I'm just wondering what the possible causes are of the noise that it's making so that I have an idea of what needs to be done to fix it. There's no way these transmissions sounded like that when the cars were new because I wouldn't tolerate that kind of transmission noise in a new car and I don't think many other people would either. There's a problem that needs to be fixed and I intend on fixing it.
Most people with a 'similar purchase' a complete service of drive components is a 'just do it'.
A glance at your original post - 'buzzing all gears requiring light throttle' and all six gears might have been thought a clutch issue maybe. The expected 'rattle' from the light wheel I doubt is usually experience all RPM in all gears - get someone to drive it. Everything mentioned earlier including mine is 'speculation'.
Last edited by WVZR-1; Jun 22, 2018 at 07:03 AM.
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From: NEwhere Ohio
My trans noise was worse in 1st during WOT - but i liked the angriness of it.
It would also happen if ‘lugging’ the engine up a hill under load in ‘too high of a gear’. I treated that as a message to downshift as its not good to lug an engine in too high of a gear for the driving situation.
lastly, the neutral/ clutch disengaged was a light knocking. My noise either wasnt that bad or i wasnt bothered by the rocks in a can noise.
its not often i have motor idling in neutral. Maybe my slightly more aggressive cam idle characteristics drown out the noise ?
I recommend posting a video.
btw WVZR-1 brings up a valid point. My 93 has a service transmission with a blue tag and remanufactured for GM plaque sticker on the side....
It would also happen if ‘lugging’ the engine up a hill under load in ‘too high of a gear’. I treated that as a message to downshift as its not good to lug an engine in too high of a gear for the driving situation.
lastly, the neutral/ clutch disengaged was a light knocking. My noise either wasnt that bad or i wasnt bothered by the rocks in a can noise.
its not often i have motor idling in neutral. Maybe my slightly more aggressive cam idle characteristics drown out the noise ?
I recommend posting a video.
btw WVZR-1 brings up a valid point. My 93 has a service transmission with a blue tag and remanufactured for GM plaque sticker on the side....
Last edited by dizwiz24; Jun 22, 2018 at 09:42 AM.
Melting Slicks
Joined: Apr 2007
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Yes, I heard the rattle before I bought it but it seems louder now, probably because I'm paying more attention to it. I'm just wondering what the possible causes are of the noise that it's making so that I have an idea of what needs to be done to fix it. There's no way these transmissions sounded like that when the cars were new because I wouldn't tolerate that kind of transmission noise in a new car and I don't think many other people would either. There's a problem that needs to be fixed and I intend on fixing it.
The ZF is a great transmission, the "rock crusher" M22 GM had behind muscle cars had gear noise as well; hence the name "rock crusher" but was the strongest tranny for a manual car they had at one time.
Changing the fluid should involve a synchromesh; end of story no matter what brand. I doubt that is the source of your problem however if you notice the noise goes away when you engage the clutch. Change the fluid first and see however.
Last edited by 856SPEED; Jun 23, 2018 at 08:59 AM.
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I will tell you with a high degree of certainty these are noisy transmissions from the factory. When these cars were new, GM''s solution was to install an extremely heavy dual mass sprung FW to dampen the noise caused from from the engine pulses when mated to this German manual box. These cars have obviously aged with a limited source of OEM parts, and the FW is no exception. The aftermarket FW's are mainly single mass components unlike the factory dual mass and that is what we have to install for new clutch jobs. More than likely, that is your issue. "Fixing" it will be a daunting task. Unless you find a dual mass FW or have the shims installed. Others have opted for a steel single mass to help with that. It's better for noise, but at the price of more sprung weight.
The ZF is a great transmission, the "rock crusher" M22 GM had behind muscle cars had gear noise as well; hence the name "rock crusher" but was the strongest tranny for a manual car they had at one time.
Changing the fluid should involve a synchromesh; end of story no matter what brand. I doubt that is the source of your problem however if you notice the noise goes away when you engage the clutch. Change the fluid first and see however.
The ZF is a great transmission, the "rock crusher" M22 GM had behind muscle cars had gear noise as well; hence the name "rock crusher" but was the strongest tranny for a manual car they had at one time.
Changing the fluid should involve a synchromesh; end of story no matter what brand. I doubt that is the source of your problem however if you notice the noise goes away when you engage the clutch. Change the fluid first and see however.
Race Director
Joined: Sep 2001
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From: NEwhere Ohio
If if the noise goes away when you engage the clutch wouldn't that mean the problem is in the trans? When you engage the clutch the input shaft stop spinning. How exactly does the Dual Mass flywheel stop the trans noise? I don't know how a dual Mass flywheel Works which is why I'm asking. Those flywheels aren't available new anymore, all I can find are used ones on eBay. From what I understand they wear out over time. What exactly goes bad in them and how do you check a used one to see if it's still good?
shimming is the way to go (cure 90% of the noise) but if you dont think you will be happy then you need the dual mass
start with trans fluid
Melting Slicks
Joined: Sep 2003
Posts: 2,270
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From: N. Babylon NY
IMHO the Red-Line MT-85 helped to quiet down some of the noise when I was using the light weight aluminum flywheel. I am now converting to a 4L80e. I have the ZF Doc shim kit (brand new) that I was going to use. If you want to buy it-PM me.
Steve
Steve
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Another thing I noticed is that the trans isn't quite as noisy when it's cold. It's still noisy but not quite as bad as when it is after it warms up. I wonder if it's from the oil thinning out or from case expansion or maybe a combination of both. I plan on doing a fluid change later today because I have no idea when it was last changed by the previous owner and also because I have no idea what kind of fluid is in it. God I hope it doesn't have ATF in it. I went to the parts store and got some Pennzoil synchromesh oil because for one I've seen a lot of posts from people on here in other ZF threads that says it works great and for two because it's a lot cheaper than the GM oil.
Race Director
Joined: Sep 2001
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From: NEwhere Ohio
Look for bronze flecks in the fluid - unrelated to the noise issue - but the more you see, the more wear on your synchros - and could also be result of the previous owner running the wrong fluid or not changing it.
its normal to several (3 or 4) bronze flecks.
it is not normal to have the fluid come out sparkly....
you arent mentioning notchy shifting or grinding gears so im not expecting there to be a lot.
its normal to several (3 or 4) bronze flecks.
it is not normal to have the fluid come out sparkly....
you arent mentioning notchy shifting or grinding gears so im not expecting there to be a lot.
Melting Slicks
Joined: Sep 2003
Posts: 2,270
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From: N. Babylon NY