Without a doubt!
MN6 vs MN12 Questions
Thread Starter
Burning Brakes
Joined: Aug 2004
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MN6 vs MN12 Questions
I have a '98 vert 6sp with trans problems. I can replace my old MN6 with a new MN12, LS6 clutch kit, master and slave cyls. I will not be changing my 3.42 diff. How is the MN12 different from the MN6. Gear ratios? Beefier parts? S/S shift forks? Is the MN12 a better trans? Thanks, Doug
Burning Brakes
Joined: Apr 2002
Posts: 798
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From: Manchester NH
The M12 has lower gears (higher numeric ratio) than the M6 for gears 1-3. Fourth is the same as M6 at 1:1. I do believe the two overdrive gears are also lower on the M12, but I can't recall for sure. An M12 with a 3.42 rear end is roughly the equivalent of using a 3.8 rear end with an M6 trans (somewhere between a 3.73 and 3.90).
The other main difference is that the gears are spaced further apart on the M12 due to the LS6 having a wider bandwidth than the LS1.
I don't kno whether the M12 has any beefier parts. It really jwouldn't need to, as the rear end and output shafts seem to fail before any trans. parts (as a result of excess power, that is).
-Pete
The other main difference is that the gears are spaced further apart on the M12 due to the LS6 having a wider bandwidth than the LS1.
I don't kno whether the M12 has any beefier parts. It really jwouldn't need to, as the rear end and output shafts seem to fail before any trans. parts (as a result of excess power, that is).
-Pete
Safety Car
Joined: Sep 2001
Posts: 4,411
Likes: 1
From: Wilmington NC
Originally Posted by DRR
I have a '98 vert 6sp with trans problems. I can replace my old MN6 with a new MN12, LS6 clutch kit, master and slave cyls. I will not be changing my 3.42 diff. How is the MN12 different from the MN6. Gear ratios? Beefier parts? S/S shift forks? Is the MN12 a better trans? Thanks, Doug
The MN12 is lower in all gears except 4th.(1 to 1)
The MN12 is the equivalent of changing to a 3.90 differential and should be well worth it.
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Safety Car
Joined: Sep 2001
Posts: 4,411
Likes: 1
From: Wilmington NC
Originally Posted by DRR
Any one out there know the factual difference between M12 and MN6. I would like to do this right the first time. Doug
What do you mean by factual?
Ratios? Performance differences?
Here is some more information:
http://www.z06vette.com/forums/archi...ex.php/t-37054
Thread Starter
Burning Brakes
Joined: Aug 2004
Posts: 770
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[QUOTE=Richin Chicago]What do you mean by factual?
Ratios? Performance differences?
I am looking at replacing my '98 MN6. It has several weak points, alum shift forks, stamped slider keys, and weak syncronizers. So, I am trying to find out if these problems are corrected on the new M12. I am not looking for opinions, only verifiable facts. Thanks, Doug
Ratios? Performance differences?
I am looking at replacing my '98 MN6. It has several weak points, alum shift forks, stamped slider keys, and weak syncronizers. So, I am trying to find out if these problems are corrected on the new M12. I am not looking for opinions, only verifiable facts. Thanks, Doug
Melting Slicks
Joined: Dec 2000
Posts: 2,204
Likes: 5
From: Bethlehem PA
St. Jude Donor '03-'05-'06-'08-'10
I just had the Vette Doctors change out my MN6 for a M12 which with my 4.10 rear provides awesome performance in the lower three gears. It is the lower three gears where the difference is. I waited until I had to change or repair my MN6 before I did this; I also went ahead at that time and changed out my Z06 clutch and slave to an Exedy. I haven't stopped smiling since these changes. Good luck with your choices.
Joe
Joe
Pro
Joined: Mar 2002
Posts: 632
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From: Enterprise AL
MN6 MN12
1st 2.66 2.97
2nd 1.78 2.07
3rd 1.30 1.43
4th 1.00 1.00
5th 0.74 0.84
6th 0.50 0.57
The MN 12 transmission to the best of my knowledge does not have higher grade materials than the same year MN6 units. Any improvements incorporated into either were also incoporated into the other, things such as the improved shifter rod, blocker rings etc.
The MN12 is a wide ratio transmission, the ratios were selected to take advantage of the LS6 power curve and higher RPM capabilities.
However, the LS1 power curve is very close to the LS6 below 4500 RPM, so I think the LS1 will do very well with the new ratios throughout the RPM range. Your will notice your RPM will be about 300 higher in 6th when on the highway cruising, and that may improve your passing /acceleration potential.
The clutch was improved for the Z06 in 2002. I'm not absolutely certain if it was improved in the 2001 Z06 model or not. I'm assumming it was, then upgraded again when the LS6 went to the 405 HP in 2002.
So as others have already said... go for it.
zo6vettepilot
1st 2.66 2.97
2nd 1.78 2.07
3rd 1.30 1.43
4th 1.00 1.00
5th 0.74 0.84
6th 0.50 0.57
The MN 12 transmission to the best of my knowledge does not have higher grade materials than the same year MN6 units. Any improvements incorporated into either were also incoporated into the other, things such as the improved shifter rod, blocker rings etc.
The MN12 is a wide ratio transmission, the ratios were selected to take advantage of the LS6 power curve and higher RPM capabilities.
However, the LS1 power curve is very close to the LS6 below 4500 RPM, so I think the LS1 will do very well with the new ratios throughout the RPM range. Your will notice your RPM will be about 300 higher in 6th when on the highway cruising, and that may improve your passing /acceleration potential.
The clutch was improved for the Z06 in 2002. I'm not absolutely certain if it was improved in the 2001 Z06 model or not. I'm assumming it was, then upgraded again when the LS6 went to the 405 HP in 2002.
So as others have already said... go for it.
zo6vettepilot
Thread Starter
Burning Brakes
Joined: Aug 2004
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Thanks to all for the advise and info. The latest info I found today is from Tom @ Fitchners and he found a new part # for the M12. He says this means that it was changed/upgraded. In what way is unknown. The part # for this 2nd design is 12589534. Problem is that there are 10 of the old #12561852 left in Lansing and the new ones won't be available until the old one are gone. Meanwhile my search for info go on. Doug
Former Vendor
Joined: Apr 2001
Posts: 2,719
Likes: 3
From: Anderson Indiana
The old part # 12561852 uses silicone to seal the tail housing to the main case,which is prone to leak eventually. The new part # 12589534 uses a gasket between the two halves and NO silicone. Othger than the gasket/silicone the units are the same.
Thread Starter
Burning Brakes
Joined: Aug 2004
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Thanks Rodney. I was hoping there would be improvement in the weak spots. (alum shift forks, composite blocker rings, stamped slider keys, weak syncronizers) I am still undecided as to go with your rebuild or a new M12. Doug
Melting Slicks
Joined: Jul 2004
Posts: 3,353
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From: Richmond Hill Ontario
Here is a different perspective from an old drag racer. My 04 vert is a stocker so this is not based on experience with my vette. I have found that for stock displacement/output motors, the MN12 gear ratio's (higher numeric numbers) work best as they help put the motor into the power band quicker and make use of the stock output better for quarter mile usage. When you start building stroker motors or just stock displacement engines with serious torque, I found that the MN6 type gear ratios (lower numeric numbers) worked best as they would allow the motor to grunt and work through the power band.
For a stocker go with the MN12, if you plan on putting some serious torque and hp into your ride ??? You may want to reconsider. Just a different perspective and my .02
Best of luck in your decision.
Tino
For a stocker go with the MN12, if you plan on putting some serious torque and hp into your ride ??? You may want to reconsider. Just a different perspective and my .02
Best of luck in your decision.
Tino
Resident moron
Joined: Jun 2003
Posts: 4,746
Likes: 20
From: Assachusetts
As I mentioned in my PM, definitely give Rodney a good consideration. In the end you'll have a stronger and more reliable transmission. And it'll cost less than a new M12 or M6. What's there to lose?
Dope
Dope
Intermediate
Joined: Oct 2003
Posts: 37
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From: Birmingham AL
Rodney
Originally Posted by Dope
As I mentioned in my PM, definitely give Rodney a good consideration. In the end you'll have a stronger and more reliable transmission. And it'll cost less than a new M12 or M6. What's there to lose?
Dope
Dope
