Zturd

iTrader: (12)

OK I've been looking for a built transmission to put in my 2000 FRC. Right now I have a MN6 in the car factory. I came across a member willing to sell me his M12 built tranny minus hardened main shaft. Curious as what peoples opinion of putting a M12 tranny in as opposed to the MN6 with 4.10 rear gears. Heres the gearing of the two transmissions.

LS1/MN6 LS6/M12
1st Gear 2.66:1 2.97:1
2nd Gear 1.78:1 2.07:1
3rd Gear 1.30:1 1.43:1
4th Gear 1.00:1 1.00:1
5th Gear 0.74:1 0.84:1
6th Gear 0.50:1 0.56:1
Reverse 2.90:1 3.28:1

Just give your opinion will it hurt at the track or help, pro's and con's of either will be helpful. Thanks

Bruce

Shoaf85

iTrader: (9)

I would go ahead and do it, honestly because most of the n/a vettes that are fast are mainly Z06's wether or not the tranny gearing has much to do with it or not, I know it definately can't hurt! The biggest difference will probably be making the car easier to launch since the first gear shorter,and the rest of the shifts will keep the engine in the powerband more so than teh MN6 will. I think at your power level it would be ideal and if you change your setup later on down the road then all you would have to do is change your gear back down to adjust for the power you make!.

BTW Zturd not to get OT but what is your best 1/8 mile e.t./speed?

Zturd

iTrader: (12)

I honestly forget off the top of my head for the 1/8th and mph. I want to say highest mph is around 98.74ish MPH and the ET around 7.205ish time. Just click on my name and search for threads started by me you'll see them in this section. Hope that helps!

02ZOh6

I'd ask robz about 4:10's with the mn12. I'm pretty sure hardcore racers shy away from that set-up for fear of running out of gear. I'm not 100% though.

Zturd

iTrader: (12)

I sent him a PM on CF.net He replied with saying he would prefer the MN6 though the M12 is easier to 60ft. I'm a bit torn with what to do here. I like the slightly lower 2nd gear for out on the street. However at the track where I'm actually going to run the car considerably more it could become a PIA. I feel i'm not out far enough on my 1-2shift as it is and this would shorten that and the so forth down the track. My opinion of you can get the car to need shifted 1-2 after the 60ft the 2-3 after the 330ft and hold 3rd to just past the 1/8th gets a well rounded and performing car. I've just been looking rather hard for a built MN6 and not coming up with one.

Someone stated that RPM transmissions are not recommended to run the hardened mainshaft in drag cars due to the flex can be a good thing????

02ZOh6

Maybe you can work the tire size (height) a little to fine tune your gearing? I'm not sure how much room you have but perhaps it's a possibility. As far as the hardened shaft, I can see their point. Same school of thought as racers debating dr vs. slick use way back. Slicks absorbing the shock on the drivetrain due to the flexibility of the sidewall as opposed to the dr's stiff sidewall. Sometimes I guess it's good for things to give a little.

BlownVette 2001

iTrader: (2)

If you have a lot of engine mods I would stick with the stock 3.42 and MN6 tranny..

Some guys have done the 5th and 6th gear upgrade (ratio) change so there is not such a big drop off.

Zturd

iTrader: (12)

I already have the 4.10 rear in my car for the better part of a year now. Happy with the results with the MN6 in the car but need to put a better transmission in now. I came across a good deal on a MN12 but worried it could actually hurt the car slightly at the track/street.

BlownVette 2001

iTrader: (2)

You'll have way to much gear.

nickolbag

iTrader: (2)

4th gear ratio is the same in both so you would be the same speed when you are in 4th. right?


Did he say anything on improved 1/4 times with the m12?? thats all i really want to know.

02ZOh6

[QUOTE=nickolbag;8601959]I'm not sure if they are the same The first three are different though,no? The M12 will be in 4rth earlier than the M6, I would think that depending on the hp level of the car it could potentially run out of gear earlier (M12 car). I could very well be wrong. I'd like to hear someone else's take on this.

Shoaf85

iTrader: (9)

Both the MN6 and MN12 have a 1:1 4th gear ratio so inevitably both transmissions will mph exactly the same in 4th, now the post above is correct about being in 4th earlier with the MN12 vs MN6 which is true, but the main thing is that the torque in 1st-3rd will physically be greater due to more gear in the MN12 and if you can get it too hook and bang your shifts then that is what drag racing is all about. If the OP has enough rpms to carry it through the 1/4 I personally think it(MN12) would be for the better!

BlownVette 2001

iTrader: (2)

I agree with ya, but I hope he can shift quick enough and if it hooks I hope he has a beefed up enough drive line to handle it or else there will be a lot of carnage.

Most guys running FI try to reduce there gear and save there drive line from the stress.

coanan

iTrader: (7)

Have you posted this on the Corvette Forum in the Z06 section, if not do it.
I've read that a M12 with 3.42; 1,2,3rd gears are like a MN6 with 3,90s in 1,2,3rd.
M12 with 4.10s, better be real quick with the shift or you'll be bouncing off the rev. limiter in 1,2

pittman

iTrader: (1)

Hey Z,
I think you need to do whatever will make you slower than me this season !!!
Pit

Zturd

iTrader: (12)

I dont think that will be difficult with your future mods

pittman

iTrader: (1)

Man, I do think that tranny combo would be a bit steep, but I think RobZ was running that setup with good results even if he didn't prefer it. I know he has tried them all.
My 390 with the M12 does come up quick but I don't think it would be too much for you to master with a few runs. Personally, I would go for it !!
Pit

Zturd

iTrader: (12)

Well my final thinking is coming down to this.

The car would 60ft better.
I would end up in 4th gear sooner-slightly hurting 8th mile mph and maybe ET
I will then drop to a lower mph/rpm in 4th due to the sooner shift and have to pull through 4th longer. This will increase MPH but I do feel its going to be a slight negative effect on ET versus the MN6 trans gear ratios.
I like the idea of being in 1st gear longer not less. The more MPH you can get out of 1st going into 2nd really makes things happen in the 330ft and thats where the ET really happens. You can make it there quick but I think I would have some downfalls to deal with.

At this point I think i'm going to steer away from the M12 for now and look into either having my transmission beefed up and or a built RPM/SixSpeedInc trans to put into the car and have my trans checked over before selling.

I want 10.8's this year not 11.1's. Bad enough the cage is going in upping the weight. However my 5pt is only going to weigh around 40lbs with a driverside swing out/removable bar. Going to be a 1 off. Plus it will be removable in about 30min's and never know it was there with a carpet replace

nickolbag

iTrader: (2)

So if you do a rental day you can pull the cage and shed the extra weight in no time? Thats pretty cool. Do you think you can pick up 2 tenths on driving alone?

pittman

iTrader: (1)

Man Z, all that thought makes my head hurt
You really need to get outside and melt some snow !! I think all the loss you figured in would be made up with the low 1.4 sixty foot you could pull ! I picked up .16 in my sixty foot and 1 mph with my M12\390 ,
all in hot weather over my best cold air time. Just my 2 cents...
Pit