ZF 6spd Rattle Help.

2120 Views 17 Replies 7 Participants Last post by olddog, Jan 10, 2008

MAVEN

Discussion Starter · May 30, 2007

Alright guys Ive got the F&I managers '91 coupe in my bay and hes complaining of a knocking. Its your typical ZF gear rattle, no worse than any other one Ive ever heard, I already filled the trans with some Castrol TWS 10-60 and as expected it got marginally better. The owner however is completely....well concerned with this. Ive told him its normal, and not detremental but he doesnt like it. Wants it gone. I recommended a full tuneup(its a 91 with 51k miles and no service ever save for oil/air changes) and told him this would help an additional small amount.

My question is, have any of you ever replaced the dual mass flywheel? How long do these flywheels actually work for?? How loud was this gear rattle when the cars were new?
They stopped making them the year I started in the dealership and Ive never had to actually fix this problem before, usually the oil and "normal" explanation has been enough.
So whats the concensus on installing a new OE flywheel??

Thanks.

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olddog

· #2 · May 30, 2007

Maven,

I replaced the dual mass with another dual mass flywheel on a 92 stroker - - the trans still rattled a bit and that is just the nature of the beast.

If you put a single mass flywheel in the car it will sound very loud. Just have to accept the fact that he has the strongest trannie ever put in a Vette and it will make some noise.

Only way around it is an automatic.

AK's Z06

· #3 · May 30, 2007

MAVEN said:
Alright guys Ive got the F&I managers '91 coupe in my bay and hes complaining of a knocking. Its your typical ZF gear rattle, no worse than any other one Ive ever heard, I already filled the trans with some Castrol TWS 10-60 and as expected it got marginally better. The owner however is completely....well concerned with this. Ive told him its normal, and not detremental but he doesnt like it. Wants it gone. I recommended a full tuneup(its a 91 with 51k miles and no service ever save for oil/air changes) and told him this would help an additional small amount.

My question is, have any of you ever replaced the dual mass flywheel? How long do these flywheels actually work for?? How loud was this gear rattle when the cars were new?
They stopped making them the year I started in the dealership and Ive never had to actually fix this problem before, usually the oil and "normal" explanation has been enough.
So whats the concensus on installing a new OE flywheel??

Thanks.

On my 1995, I would get a intermitten knocking sound when it was hot out, which started at around 19K miles. That C4 was driven up and down the east coast when I was doing the Nuclear outages at various plants, and I put 110K on the OEM drivetrain. When I had it changed out, the shop could not believe how well the dual mass flywheel looked. It wore very well, now mind you I didn't beat the **** out of it but that car saw everyday driving for 5 years. They replaced everything w/OEM parts, rubber in 3rd was no problem with a stock drivetrain.:thumbsup:

-=Jeff=-

· #4 · May 31, 2007

Yeah the Dual mass could cause some of the noise. the only other option would be to pull the balck tag trans out of it ans swap it with a Blue tag trans. the Blue tag had MORE of a helical cut to quiet the noise down. the black tag had less of a helical cut.. the trade off was torque.. the blck tag was rated for 450ftlb and the blue tag at 400ftlb

MAVEN

Discussion Starter · #5 · May 31, 2007

Thats what I expected, just wanted to hear it from some people who actually remembered what they were like new before I recommended a $2000 partial fix.

Thanks guys.

olddog

· #6 · May 31, 2007

I have BOTH trannies and a new 'blue' sitting at the shop in the crate. GM auctioned all of them off not long ago. It too rattles just not as much: trust me on this one.

ALZR1

· #7 · May 31, 2007

olddog said:
I have BOTH trannies and a new 'blue' sitting at the shop in the crate. GM auctioned all of them off not long ago. It too rattles just not as much: trust me on this one.[/QUOT

I bought A blue tag from GM and it sounded like super charger,the noise got greater with every gear change.the noise is coming from the input shaft bearing.
It's normal for the ZF to make noise,now if you have A bad flywheel the gear
chatter is really loud.Installing A dual mass flywheel will cure the problem.

AL.

MAVEN

Discussion Starter · #8 · May 31, 2007

olddog said:
trust me on this one.

I do, thats why I asked ya.

cheetah

· #9 · May 31, 2007

What did TAC say? If TAC says it's normal, how's your F&I guy going to argue with that? Can't fix it, if it ain't broke.

MAVEN

Discussion Starter · #10 · Jun 1, 2007

cheetah said:
What did TAC say? If TAC says it's normal, how's your F&I guy going to argue with that? Can't fix it, if it ain't broke.

TAC??

those guys are well..... ineffective at best. and would laugh(or cry, not sure which) if you called in on a '91 Vette.

MAVEN

Discussion Starter · #11 · Jun 1, 2007

I knew the answer, just needed backup.

cheetah

· #12 · Jun 2, 2007

MAVEN said:
TAC?? those guys are well..... ineffective at best. and would laugh(or cry, not sure which) if you called in on a '91 Vette.

There are ineffective people everywhere. Even where you work. Sometimes you get somebody who knows what they are talking about. Just because it's out of warranty, doesn't mean they don't have information about it.

olddog

· #13 · Jun 2, 2007

That is why I keep a new, ZF in my shop in the crate - - one day someone will need one and the re-build can only be done by three in the country. Parts are hard to come by.

I figure that someone will be buying it when they find the cost of a rebuild usually starts at 2500 bucks . . :thud:

MAVEN

Discussion Starter · #14 · Jun 2, 2007

cheetah said:
There are ineffective people everywhere. Even where you work. Sometimes you get somebody who knows what they are talking about. Just because it's out of warranty, doesn't mean they don't have information about it.

Cheetah, I totally agree with what you're saying and sincerely mean no disrespect but the fact is this car is 16yrs old and this trans hasnt been used in any platform in nearly a dozen years, TAC doesnt have any more resources at their fingertips on this particular case than I do, in fact they have less, because I can freely ask other knowledgeable enthusiasts of their experiences and they cant. Secondly the just because "TAC says it's normal" doesnt mean my customer cant argue. And the fact that his warrarnty is up is precisely why the customer has an even stronger position, its his money, not GM's. "Can't fix it, if it ain't broke." is an untrue euphemism that is counterproductive if used in a situation as this. This gentlemans car is making unacceptable levels of undesirable noise. Even if it "aint broke" it certainly aint right, and even though he's an employee if I told him anything even on the same level as that....maybe "inherent characteristic", " acceptable mechanical acoustics" or " commercially quiet" he would be on the phone with Charlie Kerbeck so fast my head would spin.
Any good shop or technician takes care of the customers complaint they dont just fix whats broken, Ive got a very high Customer Satisfaction Rating (and intend to keep it that way) and this why this gentleman came to me even though I actually work in the Pontiac-GMC shop and not the Vette shop.

Truth be told, the Vette shop gave him a second opinion(on my request, based on the cost of the repair and the likelihood it wont remedy the issue 100%) and they told him.....It needs an ENGINE.

Thanks for all the responses guys, lets just hope that the lash in the trans isnt so high that even a flywheel wont help.

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cheetah

· #15 · Jun 3, 2007

I'm sorry. I thought you said it was making normal noise inherent of the transmission, not unacceptable levels that needed to be addressed. My mistake.

Just thought of something, do the flywheels crack on those? That would cause one helluva rattle that someone might mistake for an internal engine noise.

olddog

· #16 · Jun 3, 2007

If I understand you correctly, the thing has been dormant a long time - - check for pitting which WILL make it worse.

MarkusZF

· #17 · Jan 10, 2008

-=Jeff=- said:
Yeah the Dual mass could cause some of the noise. the only other option would be to pull the balck tag trans out of it ans swap it with a Blue tag trans. the Blue tag had MORE of a helical cut to quiet the noise down. the black tag had less of a helical cut.. the trade off was torque.. the blck tag was rated for 450ftlb and the blue tag at 400ftlb

Naah i love that sound , thats why i have a black tag zf6 , took me alot of time finding a car with that here,. :thumbsup:

olddog

· #18 · Jan 10, 2008

Just remember I have a new ZF in the GM crate for sale - - -

I liked the early ones and to hell with the noise: it is a Vette and not a Rolls!!

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