ZF Option
Burning Brakes
Joined: Dec 2001
Posts: 777
Likes: 1
From: Fort Worth Texas
I will look for the the spread sheet that has what all the 96 codes are. I recieved this information from the GrandSport Registry web site for 96 LT4 C4's. GM only used the ZF for 6 speed manual trans so it is a double code
When GM went with the 6 speed (ZF)in the late 80's they may have listed the codes different.
Le Mans Master
Joined: Jun 2006
Posts: 5,642
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From: One day you're a Comet...the next day you're dust... Arkansas
Race Director
Joined: Oct 2005
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From: Rolla Missouri
2021 C4 of the Year - Unmodified Finalist
St. Jude Donor '10 thru '25
I sure don't want to "stir" things up anymore. But I agree there are the two codes (MN6 and ML9)
Here is what I think would be a good explanation for it:
Having both codes is one way of more efficient inventory management
MN6 = 6-speed transmission.
ML9 = ZF6.
It just so happens that the ZF6 was the ONLY transmission available on the C4.
But auto manufacturing (or inventory control) is a very complicated procedure. In this case, they were easily prepared to use an alternate 6-speed transmission if one was available or designed.
As SurfnSun said, the MN6 code is still used on the C5 and C6. It just means they have a 6-speed transmission but no ZF6, so the actual transmission code is something else.
Oh yeah, there could even be some corporate political issues involved too. Remember GM is a very large and complex organization
Here is what I think would be a good explanation for it:
Having both codes is one way of more efficient inventory management
MN6 = 6-speed transmission.
ML9 = ZF6.
It just so happens that the ZF6 was the ONLY transmission available on the C4.
But auto manufacturing (or inventory control) is a very complicated procedure. In this case, they were easily prepared to use an alternate 6-speed transmission if one was available or designed.
As SurfnSun said, the MN6 code is still used on the C5 and C6. It just means they have a 6-speed transmission but no ZF6, so the actual transmission code is something else.
Oh yeah, there could even be some corporate political issues involved too. Remember GM is a very large and complex organization
Le Mans Master
Joined: Jun 2006
Posts: 5,642
Likes: 5
From: One day you're a Comet...the next day you're dust... Arkansas
Yeah, you're right. I think the key is to avoid having your self worth and manhood attached to Corvette minutiae. It's not the end of the world to make or admit a mistake. It's just that some people never learn that.
Last edited by BADDUCK; Apr 1, 2007 at 10:31 AM.
Thread Starter
Le Mans Master
Joined: Nov 2006
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From: Greenwood Indiana
2021 C4 of the Year - Modified Finalist
C4 of Year Finalist (appearance mods) 2019
The T56 must not be too bad since the C-5s & 6s are rated with higher HP & torque. What are the gear ratios of a "Blue Tag ZF6"?
Team Owner
Joined: Aug 2000
Posts: 40,156
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From: San Pedro CA
However, in all fairness, the LSx is putting out quite a bit of power, but so are many 383s, ZR1s and Callaways.
Last edited by bogus; Apr 1, 2007 at 02:04 PM. Reason: just noticed a typo.
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Melting Slicks
Joined: May 2001
Posts: 3,014
Likes: 18
From: Raleigh, NC
The T56 is a great transmission. There are LS1/LT1 F-bodies making over 1000 RWHP through a stock T56. It's just like the ZF6, if you use it properly, it will last. If abused by poor shifting practices, it will fail.
It's also much more common than the ZF6 in our cars, cheaper to build, lighter, easier to find replacement parts for, and has 10 times the clutch options we do.
Ya, sounds like it sucks to me.
It's also much more common than the ZF6 in our cars, cheaper to build, lighter, easier to find replacement parts for, and has 10 times the clutch options we do.
Ya, sounds like it sucks to me.
Race Director
Joined: Sep 2000
Posts: 17,298
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From: The Top of Utah
Originally Posted by SurfnSun
Attacking Bogus was just dumb.
Originally Posted by SurfnSun
The only thats is pathetic is that you can't admit to being wrong. Whats poetic is that you shot your mouth off when you didn't know what you were talking about.
Whats poetic is that you shot your mouth off when you didn't know what you were talking about.I posted a page from my parts book, and I have provided a link to the Forum's own speedo chart where all the six speeds are listed as the ML9. I have a C4 parts book, 1984 through 1996, dated March, 2000, on CD that lists all of the C4 six speed transmissions as having the RPO number of ML9. I am unable to copy from that CD. I don't know what "MN6" is or where it came from, but I see no deviation from ML9 being the RPO code for the C4 six speed trans. Could it be a model number ZF uses for that trans? I WILL admit I'm wrong, if I am.
I have some responses for some other comments made, but lets let sleeping dogs lie.
RACE ON!!!
Team Owner
Joined: May 2002
Posts: 24,337
Likes: 25
From: San Diego , CA Double Yellow DirtBags 1985..Z51..6-speed
Team Owner
Joined: May 2002
Posts: 24,337
Likes: 25
From: San Diego , CA Double Yellow DirtBags 1985..Z51..6-speed
Melting Slicks
Joined: Feb 2006
Posts: 2,240
Likes: 0
From: Cleveland OHIO
think the biggest problem with the T56 in the C5/6 is that the tranny is rear mounted. The linkage is long and could bind, causing poor shifts even when the driver does everything right.
Now that is Bogus information. Pun intended.
Could bind ??
Now that is Bogus information. Pun intended.
Could bind ??
Burning Brakes
Joined: Dec 2001
Posts: 777
Likes: 1
From: Fort Worth Texas
It was not my intention to attack bogus. If that is the way it was perceived, I apologize.
I do know what I'm talking about. I posted backup for my statement. I can, and I will, admit I am wrong, if it can be shown by a greater authority, than the often in error, bogus, that I am.
I posted a page from my parts book, and I have provided a link to the Forum's own speedo chart where all the six speeds are listed as the ML9. I have a C4 parts book, 1984 through 1996, dated March, 2000, on CD that lists all of the C4 six speed transmissions as having the RPO number of ML9. I am unable to copy from that CD. I don't know what "MN6" is or where it came from, but I see no deviation from ML9 being the RPO code for the C4 six speed trans. Could it be a model number ZF uses for that trans? I WILL admit I'm wrong, if I am.
I have some responses for some other comments made, but lets let sleeping dogs lie.
RACE ON!!!
I do know what I'm talking about. I posted backup for my statement. I can, and I will, admit I am wrong, if it can be shown by a greater authority, than the often in error, bogus, that I am.
I posted a page from my parts book, and I have provided a link to the Forum's own speedo chart where all the six speeds are listed as the ML9. I have a C4 parts book, 1984 through 1996, dated March, 2000, on CD that lists all of the C4 six speed transmissions as having the RPO number of ML9. I am unable to copy from that CD. I don't know what "MN6" is or where it came from, but I see no deviation from ML9 being the RPO code for the C4 six speed trans. Could it be a model number ZF uses for that trans? I WILL admit I'm wrong, if I am.
I have some responses for some other comments made, but lets let sleeping dogs lie.
RACE ON!!!
ML9=ZF 6 Speed trans
This is my RPO codes for my 96 LT4 ZF 6 Speed manual.
Codes that are under the lid behind the passenger seat that holds the owners manual. I checked these 96 codes.
Have a Nice Day.
Team Owner
Joined: Aug 1999
Posts: 24,017
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St. Jude Donor '10
MN6 = 6 speed manual transmission car, All Corvettes since 89 use this as the manual tranny option.
ML9 = part designation. ZF in this case, as listed on your sheet.
Race Director
Joined: Sep 2000
Posts: 17,298
Likes: 33
From: The Top of Utah
RACE ON!!!