Swapping M6 to M12
Melting Slicks
Joined: Sep 2003
Posts: 2,458
Likes: 105
From: Northville Michigan
Please reconsider !
The MN6 is a better trans for performance. Instead of spending you money buying and installing a MN12 trans, get yourself a set of 4.10 gears. You will be amazed at the performance increase.
I took the MN12 trans out of my Z06 and installed a MN6 with the 4.10 gears.
Good luck with your decision.
.
The MN6 is a better trans for performance. Instead of spending you money buying and installing a MN12 trans, get yourself a set of 4.10 gears. You will be amazed at the performance increase.
I took the MN12 trans out of my Z06 and installed a MN6 with the 4.10 gears.
Good luck with your decision.
.
Pro
Joined: May 2004
Posts: 531
Likes: 46
From: Tucson, AZ
Just out of curiousity, why is this a bad idea? I was always under the impression that 4.10 gears were a lot weaker than the stock 3.42's, and therefore the MN12/3.42 combo gives you the same effective gearing while maintaining stronger gears out back - Definitely correct me if I'm wrong!
Melting Slicks
Joined: May 2003
Posts: 2,851
Likes: 1
From: San Bruno Ca
Originally Posted by CaptainCrunch
Just out of curiousity, why is this a bad idea? I was always under the impression that 4.10 gears were a lot weaker than the stock 3.42's, and therefore the MN12/3.42 combo gives you the same effective gearing while maintaining stronger gears out back - Definitely correct me if I'm wrong!
Burning Brakes
Joined: Oct 2002
Posts: 797
Likes: 1
From: Sunny Earthquake Country, USA On the Left Coast (which is becoming more Right!)
My vote is MN6!...
Originally Posted by DRR
Anything needed to adapt the Z trans into a C5? I wish there was a way to use the temp sensor. Doug
The downside is mileage which will drop 2-3 MPG. However the 6th gear in MN6 is .50 whereas in the MN12 it is .62 which helps a little in the mileage dept.
As you don't have a 550-700 RWHP car and it is probably a street machine, I think staying with the MN6 is the best bet and going with a 3.90 or 4.10 rear gear.
As mentioned above, In a given housing size the smaller the pinion the weaker the gear, but unless you increase your power significantly or do a lot of side stepping-you'll be ok.
Now the real benefit of a 3.90 or 4.10 rear gear is that the cars performance in 3rd, 4th, 5th, and 6th will really amaze you-the high (numerically) axles really liven up driving in the usual gears that you are in most of the time.
Most of us concentrate on peak HP and what the car will do in 1st gear, what about having fun with our buddy Mr. Torque the other 99% of the time!
May the BOOST be with you!
Roy
Resident moron
Joined: Jun 2003
Posts: 4,746
Likes: 20
From: Assachusetts
Originally Posted by 7.0sc SuperVette
If you put in a 3.90 gear the ratio overall in 1st gear will be essentially the same as the MN12 and the ratios in the 1st to 4th range will be closer which is better for drags, road racing and street driving.
The downside is mileage which will drop 2-3 MPG. However the 6th gear in MN6 is .50 whereas in the MN12 it is .62 which helps a little in the mileage dept.
As you don't have a 550-700 RWHP car and it is probably a street machine, I think staying with the MN6 is the best bet and going with a 3.90 or 4.10 rear gear.
As mentioned above, In a given housing size the smaller the pinion the weaker the gear, but unless you increase your power significantly or do a lot of side stepping-you'll be ok.
Now the real benefit of a 3.90 or 4.10 rear gear is that the cars performance in 3rd, 4th, 5th, and 6th will really amaze you-the high (numerically) axles really liven up driving in the usual gears that you are in most of the time.
Most of us concentrate on peak HP and what the car will do in 1st gear, what about having fun with our buddy Mr. Torque the other 99% of the time!
May the BOOST be with you!
Roy
The downside is mileage which will drop 2-3 MPG. However the 6th gear in MN6 is .50 whereas in the MN12 it is .62 which helps a little in the mileage dept.
As you don't have a 550-700 RWHP car and it is probably a street machine, I think staying with the MN6 is the best bet and going with a 3.90 or 4.10 rear gear.
As mentioned above, In a given housing size the smaller the pinion the weaker the gear, but unless you increase your power significantly or do a lot of side stepping-you'll be ok.
Now the real benefit of a 3.90 or 4.10 rear gear is that the cars performance in 3rd, 4th, 5th, and 6th will really amaze you-the high (numerically) axles really liven up driving in the usual gears that you are in most of the time.
Most of us concentrate on peak HP and what the car will do in 1st gear, what about having fun with our buddy Mr. Torque the other 99% of the time!
May the BOOST be with you!
Roy
The only valid reason for switching would be if you wanted shorter gearing and didn't want to swap out the rear end too (like say if you blew up your tranny, and needed a replacement).
Dope
Thread Starter
Burning Brakes
Joined: Aug 2004
Posts: 770
Likes: 0
Thanks, I guess. Yes, I did blow up my trans. No, I don't want to change the diff. The only real drawback of the M12 is that it uses the same 4th gear as the MM6 (1 to 1 ratio) so there is a bigger jump from 3rd to 4th. GMPP makes a close ratio 6sp, but it cost over 6K. The M12 is the same price as the MN6. The M12 ratios are- 1st/2.97, 2nd/2.07, 3rd/1.43, 4th/1, 5th/.84, 6th/.57. The MM6 ratios are- 1st/2.66, 2nd/1.78, 3rd/1.3, 4th/1, 5th/.74, 6th/.5. So the M12 vs MM6 ratio spacing is- 1st to 2nd-.90 vs .88(+.02), 2nd to 3rd-.64 vs .48(+.16), 3rd to 4th-.43 vs .3(+.13), 4th to 5th-.16 vs .26(-.1), 5th to 6th-.27 vs .24(+.03). So you could say the spacing is about the same from 1st to 2nd, bigger from 2nd to 3rd and 3rd to 4th, smaller from 4th to 5th, and about the same from 5th to 6th. Only you get into the power band quicker in 1st, for a better launch, without changing the diff. Take the car to the 1/4 mi. Same car, same driver, same temp, same RH, same launch- only diff-M12 vs MM6- which one wins? Aren't drag affects are much stronger at hi speed- (4th to 5th) So, yes I am going with the M12. Now, can anyone answer my original question? I guess I need to know if the ECM or programing is different? Thanks, Doug
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Team Owner
Joined: Sep 2003
Posts: 43,084
Likes: 33
From: Raleigh / Rolesville NC
Stick with the MN6. I have driven lots of ZO6s with Mn12s and the best thing I think these guys could do is put in a mn6.
4.10 maybe good for drag racing but not a chance for road racing. The corvette has soo much torque and the power band is so large the lower 4.10 gear will not help. also 4.10s limit your top speed to about 150 mph in 5th. Plus all the shifting you have to do. each time you shift you loose power. The less shifting the better for most ppl.
I have a 400 rwhp coupe with a mn6 and bumpped red line to 6750. I do 150 in 4th at 6700. ( on the track of course no street racing for me)
Gm also makes a 3.72 road racing rear end.
4.10 maybe good for drag racing but not a chance for road racing. The corvette has soo much torque and the power band is so large the lower 4.10 gear will not help. also 4.10s limit your top speed to about 150 mph in 5th. Plus all the shifting you have to do. each time you shift you loose power. The less shifting the better for most ppl.
I have a 400 rwhp coupe with a mn6 and bumpped red line to 6750. I do 150 in 4th at 6700. ( on the track of course no street racing for me)
Gm also makes a 3.72 road racing rear end.
Thread Starter
Burning Brakes
Joined: Aug 2004
Posts: 770
Likes: 0
Thanks for the opinion. My M12 will be here on Thursday so I won't be changing my mind.(You can read the data details and differences in my previous post) I just want to know from anyone who has done the MN6 to M12 swap if there are any issues to consider. Thanks for all the other input, but it won't help me, Doug
Burning Brakes
Joined: Oct 2003
Posts: 959
Likes: 12
From: California CA
Originally Posted by DRR
The only real drawback of the M12 is that it uses the same 4th gear as the MM6 (1 to 1 ratio)
This is the reason why you should always do your dyno pulls in 4th as it does not stress the gearbox.
Drifting
Joined: Mar 2005
Posts: 1,737
Likes: 0
From: Northern VA
Originally Posted by sprinter
This is the reason why you should always do your dyno pulls in 4th as it does not stress the gearbox.
Le Mans Master
Joined: Dec 2003
Posts: 5,561
Likes: 448
From: Atlanta metro Ga.
I also believe in the M6 - 3.90's over M12 - 3.42's combo.
That said, no, nothing special required.
I had a plan at one point to integrate an M12 temp sensor into the DIC by sharing the oil temp display. My plan was to have the two sensors switch back and forth, at say, 5 sec. intervals, using a small IC circuit.
Probably would work o.k., as long as the PCM / BCM didn't freak out during the transition period between the two (would be in milliseconds / shouldn't be a problem. Maybe I'll do it one day..
That said, no, nothing special required.
I had a plan at one point to integrate an M12 temp sensor into the DIC by sharing the oil temp display. My plan was to have the two sensors switch back and forth, at say, 5 sec. intervals, using a small IC circuit.
Probably would work o.k., as long as the PCM / BCM didn't freak out during the transition period between the two (would be in milliseconds / shouldn't be a problem. Maybe I'll do it one day..
Melting Slicks
Joined: Sep 2003
Posts: 2,458
Likes: 105
From: Northville Michigan
Tommy,
The MN6 transmission keeps RPMs at or above the Torque Peak during the 2nd to 3rd, 3rd to 4th, and 4th to 5th shifts. See attached chart:
Only during the 4th to 5th shift does the MN12 keeps the RPMs above the Torque Peak.
Both transmissions suck when it comes to RPM loss on the 5th to 6th shift. In my Z06 I have had a custom 0.563:1 6th gear built and installed. As you can see by the red line in the above chart my RPMs stay above the Torque Peak on the 5th to 6th shift also.
Believe me, you will love your MN6 once you install either a 4.10 or 3.90 gear set.
.
The MN6 transmission keeps RPMs at or above the Torque Peak during the 2nd to 3rd, 3rd to 4th, and 4th to 5th shifts. See attached chart:
Only during the 4th to 5th shift does the MN12 keeps the RPMs above the Torque Peak.
Both transmissions suck when it comes to RPM loss on the 5th to 6th shift. In my Z06 I have had a custom 0.563:1 6th gear built and installed. As you can see by the red line in the above chart my RPMs stay above the Torque Peak on the 5th to 6th shift also.
Believe me, you will love your MN6 once you install either a 4.10 or 3.90 gear set.
.
Thread Starter
Burning Brakes
Joined: Aug 2004
Posts: 770
Likes: 0
Hey Pumba, Nice graph. But look close at the details. 250 rpm difference going to 3rd and 500 rpm difference going to 4th. But going into 5th the table turns and the M12 has got a 750 rpm advantage, and if you are 1/4 mileing and going over 100 mph drag is very hi, and you will feel a difference. Doug
Melting Slicks
Joined: Sep 2003
Posts: 2,458
Likes: 105
From: Northville Michigan
DRR,
Thanks for the note.
If you remember the speeds you can attain with a MN12 and a 3.42:1 final drive ratio at 6,500 rpm are as follows:
2nd - 68 mph
3rd - 99 mph
4th - 143 mph
5th - 170 mph
Now, I don't know how much rear wheel horsepower you have or what tires you are running at the drag strip, but I would guess that you barely out of 3rd gear.
So, I will stand by my suggestion of keeping the MN6 trans and spending the money on a 4.10 gear set.
Good luck with your decision.
.
Thanks for the note.
If you remember the speeds you can attain with a MN12 and a 3.42:1 final drive ratio at 6,500 rpm are as follows:
2nd - 68 mph
3rd - 99 mph
4th - 143 mph
5th - 170 mph
Now, I don't know how much rear wheel horsepower you have or what tires you are running at the drag strip, but I would guess that you barely out of 3rd gear.
So, I will stand by my suggestion of keeping the MN6 trans and spending the money on a 4.10 gear set.
Good luck with your decision.
.
Thread Starter
Burning Brakes
Joined: Aug 2004
Posts: 770
Likes: 0
You are correct about not needing 5th in the 1/4 mi. But you might have missed this when I posted it above-Thanks for the opinion. My M12 will be here on Thursday so I won't be changing my mind.(You can read the data details and differences in my previous post) I just want to know from anyone who has done the MN6 to M12 swap if there are any issues to consider. Thanks for all the other input, but it won't help me, Doug
Last edited by DRR; Jul 13, 2005 at 10:09 PM.
