danoz

I have a 2003 Z06 with a procharger and supporting mods. It would seem extremely advantageous to have stock LS1 gearing. Those of us with C5Zs shift into 4500-4600 rpm every time you shift with the exception of 5th and 6th gear, assuming your rev limiter is stock. Where as on an LS1 you progressively shift into a higher RPMs up until 5th gear. If memory serves me correctly 5200 in 3rd and 5500 in 4th thus keeping you in your power band.
So my question is, has any replaced their transmission on the blown C5Z(centrifugal type) with LS1 gearing? What kind of gains did you make in the 1/4 specifically your trap speed. Was it worth it? This just seems like a great upgrade when and if my transmission ever needs to be replaced.
If this has been discussed before would someone please give me a link to the thread, I couldn't find it on my own. Thank you in advanced.

AU N EGL

Not LS1 gearing

MN12 vs MN6

For drag racing, not really. For road racing, a few guys have made the change for a better 3rd gear.

the MN12 is better for acceleration from a dead stop

BuddhaZ06

Isn't 2nd gear the only thing different?

skyavonee

According to the Z06 FAQ, every gear except 4th is different between the MN12 and MN6.

AU N EGL

Up that 1500 rpms to shift.

For performance use shift AT RED LINE. 65-6600

SCM_Crash

In a forced induction setup, it's better to have longer gears (for road racing). But honestly, the M12 is fine. The difference between the MN6 and MN12 is like going from 3.42s to 3.90s except that the 4th gears are identical.

I think the only real advantage you might see is better economy. Forced induction or not, if you haven't changed the cam, your power band is still in the same place. Adding the forced induction to it will amplify that, but I think you're probably good with your setup. Are you planning to drag race or road race at all?

zeevette

Isn't the first gear in a MN6 a 2.66, wheras the M12's is 2.97? That would make your rear 3.42 lower (numerically) rather than higher. I've heard the std. MN6 refered by some as a "close ratio" gearbox, but the spread between 1-4 is wider than a M12, no?

danoz

I meant where you will be in the next gear after you shift. You shift at 6700 in 3rd and you will be at about 4500-4600 in 4th vs 5500 in 4th in the MN6.

This is more for drag racing. Would it atleast make a difference in the trap speed.


I have a couple of charts I will post when I get home. It shows where you will be in the next gear assuming same tire size(305/35/18) in my case, for both the MN6 and MN12. I have been debating this with my fellow vette owners here in Vegas and it just looks like it would make a noticable difference for my set up, not so much for nitrous.

SCM_Crash

What I mean is that the multiplication of the rear end and drive gear is closer to having 3.90 rear ends vs. the MN6.

For example:
MN6 with 3.42 ratio rear end - 2.66 * 3.42 = 9.0972
MN6 with 3.90 ratio rear end - 2.66 * 3.90 = 10.374
MN12 with 3.42 ratio rear end - 2.97 * 3.42 = 10.1574

In the LS6 cars, you get 500 RPM more from the motor, so the fact that the transmission would have you shifting sooner is made up for the fact that you have more room to run.

As for the ratios being closer or wider, the MN12's ratios are actually closer. I can't recall how to explain this with math, but the MN12 gearing is designed to keep the LS6 in the top 4000 RPM while the MN6 gearing is designed to keep the LS1 in the top 3500 RPM.

If this is for drag racing, stick with the MN12. You're going to get your trap speed in 4th gear. Not 5th or 3rd. The MN6 will have you top out 3rd gear at about 106 if you're still spinning to 6500. 3rd gear in the MN12 will get you to 100MPH. Either way, you're going to trap higher than that. 4th gear should get you to 145MPH. With a blower, you should be trapping in the high 120's to the low 130's. Meaning you can get into 4th gear faster with the MN12 and have a longer 1:1 (4th gear) run with the blower. Your trap should be higher (in theory) with the MN12.

At least, that's what I'm thinking it would be on paper.

zeevette

I don't know how to explain this technically, but it seems to me that the higher the number, for example 2.97 vs 2.66, then the higher your final ratio is. With both cars having 3.42 rear gears, the M12 car would be more like the 3.90 than the MN6; just the opposite of your example. M12 would (assuming equal redlines) have to shift sooner than a car with a MN6 first gear ratio. The higher numbered 1st gear in a M12 is better for fast acceleration from a stop, but you'd have to hit 2nd gear at a lower speed (redline) with a M12.

SCM_Crash

Perhaps you didn't understand the math here or anything that I said... The numbers I posted are reduction ratios.

You basically just said exactly what I said except that you added the fact that you'd shift sooner with equal red-lines.

Read my post above a little closer:

MN12 + 3.42 rear end is ~= MN6 + 3.90 rear end.

Check the math.

AU N EGL

the Close ratio gear box is the GM Motorsports transmission or the ZR1 transmission. these two are almost the same ratios

All_Motor_C5LS6

I don't see how the ZR1 tranny is anywhere near close to a MN12 tranny. The MN6 is closer to the ZR1 tranny

........ZR1 MN12 MN6
1st - 2.29 2.97 2.66
2nd - 1.61 2.07 1.78
3rd - 1.21 1.43 1.30
4th - 1.00 1.00 1.00
5th - .81 .71 .74
6th - .67 .57 .50

zeevette

See, I was hoping to avoid doing math. Sorry if I misunderstood.

AU N EGL

its not, never said it was

the MN12 was for -0-60 times the least shifting and to keep the HP in the sweet spot of 4200 to 6500 rpms

many guys like the MN6 for road race track use.

the MN12 2-3 is to low, the MN6 2-3 is great

the Zr1 ratio is perfect for a road course.

All_Motor_C5LS6

gotcha!

danoz

Sorry about the format. I wish I could find the original site where I found this. 3rd and fourth would be an improvement for me since my powerband is mostly in 5500 and up.
Probably just better in the 80 to 145 range. I wish I had limitless funds to swap out the trans with the MN6 gearing to see if I would atleast trap higher. My rev limiter at the time was 7000 when I had these charts generated. If someone knows where you can put in the gearing info and generate a chart please post it. Thanks. You guys make a good point about the MN12 being the preferred transmission. Correct me if I am wrong but doesn't the C6Z has the same gearing as the MN6?

I have 305/35/18 in the rear.

Gear LS1/MM6 LS6/M12doesn

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
Axle Ratio varies 3.42:1
Final Drive Ratio varies 1.91:1



MN12
RPM 1st Gear 2nd Gear 3rd Gear 4th Gear 5th Gear 6th Gear
500 4 6 8 11 14 21
600 5 7 10 14 16 25
700 5 8 11 16 19 29
800 6 9 13 18 22 33
900 7 10 14 21 25 37
1000 8 11 16 23 27 41
1100 9 12 18 25 30 45
1200 9 13 19 28 33 49
1300 10 14 21 30 36 53
1400 11 16 22 32 38 57
1500 12 17 24 34 41 62
1600 12 18 26 37 44 66
1700 13 19 27 39 46 70
1800 14 20 29 41 49 74
1900 15 21 31 44 52 78
2000 15 22 32 46 55 82
2100 16 23 34 48 57 86
2200 17 24 35 51 60 90
2300 18 26 37 53 63 94
2400 19 27 39 55 66 98
2500 19 28 40 57 68 103
2600 20 29 42 60 71 107
2700 21 30 43 62 74 111
2800 22 31 45 64 77 115
2900 22 32 47 67 79 119
3000 23 33 48 69 82 123
3100 24 34 50 71 85 127
3200 25 36 51 74 88 131
3300 26 37 53 76 90 135
3400 26 38 55 78 93 139
3500 27 39 56 80 96 144
3600 28 40 58 83 98 148
3700 29 41 59 85 101 152
3800 29 42 61 87 104 156
3900 30 43 63 90 107 160
4000 31 44 64 92 109 164
4100 32 45 66 94 112 168
4200 32 47 67 96 115 172
4300 33 48 69 99 118 176
4400 34 49 71 101 120 180
4500 35 50 72 103 123 185
4600 36 51 74 106 126 189
4700 36 52 75 108 129 193
4800 37 53 77 110 131 197
4900 38 54 79 113 134 201
5000 39 55 80 115 137 205
5100 39 57 82 117 139 209
5200 40 58 84 119 142 213
5300 41 59 85 122 145 217
5400 42 60 87 124 148 221
5500 43 61 88 126 150 226
5600 43 62 90 129 153 230
5700 44 63 92 131 156 234
5800 45 64 93 133 159 238
5900 46 65 95 136 161 242
6000 46 67 96 138 164 246
6100 47 68 98 140 167 250
6200 48 69 100 142 170 254
6300 49 70 101 145 172 258
6400 49 71 103 147 175 263
6500 50 72 104 149 178 267
6600 51 73 106 152 180 271
6700 52 74 108 154 183 275
6800 53 75 109 156 186 279
6900 53 77 111 158 189 283
7000 54 78 112 161 191 287

MN6
RPM 1st Gear 2nd Gear 3rd Gear 4th Gear 5th Gear 6th Gear
500 5 7 9 12 16 24
600 5 8 11 15 20 29
700 6 10 13 17 23 34
800 7 11 15 19 26 39
900 8 12 17 22 30 44
1000 9 14 19 24 33 49
1100 10 15 21 27 36 54
1200 11 16 22 29 39 58
1300 12 18 24 32 43 63
1400 13 19 26 34 46 68
1500 14 20 28 36 49 73
1600 15 22 30 39 53 78
1700 16 23 32 41 56 83
1800 16 25 34 44 59 88
1900 17 26 36 46 62 92
2000 18 27 37 49 66 97
2100 19 29 39 51 69 102
2200 20 30 41 54 72 107
2300 21 31 43 56 76 112
2400 22 33 45 58 79 117
2500 23 34 47 61 82 122
2600 24 36 49 63 85 126
2700 25 37 51 66 89 131
2800 26 38 52 68 92 136
2900 27 40 54 71 95 141
3000 27 41 56 73 99 146
3100 28 42 58 75 102 151
3200 29 44 60 78 105 156
3300 30 45 62 80 108 161
3400 31 46 64 83 112 165
3500 32 48 65 85 115 170
3600 33 49 67 88 118 175
3700 34 51 69 90 122 180
3800 35 52 71 92 125 185
3900 36 53 73 95 128 190
4000 37 55 75 97 131 195
4100 37 56 77 100 135 199
4200 38 57 79 102 138 204
4300 39 59 80 105 141 209
4400 40 60 82 107 145 214
4500 41 61 84 109 148 219
4600 42 63 86 112 151 224
4700 43 64 88 114 154 229
4800 44 66 90 117 158 233
4900 45 67 92 119 161 238
5000 46 68 94 122 164 243
5100 47 70 95 124 168 248
5200 48 71 97 126 171 253
5300 48 72 99 129 174 258
5400 49 74 101 131 177 263
5500 50 75 103 134 181 268
5600 51 77 105 136 184 272
5700 52 78 107 139 187 277
5800 53 79 109 141 191 282
5900 54 81 110 143 194 287
6000 55 82 112 146 197 292
6100 56 83 114 148 200 297
6200 57 85 116 151 204 302
6300 58 86 118 153 207 306
6400 59 87 120 156 210 311
6500 59 89 122 158 214 316
6600 60 90 123 161 217 321
6700 61 92 125 163 220 326
6800 62 93 127 165 223 331
6900 63 94 129 168 227 336
7000 64 96 131 170 230 340

SCM_Crash

I can write the a tool to generate this stuff. If I have time tomorrow, I'll do that.

zx9rgreen

These numbers aren't correct, since the mn6 and mn12 share the same 4th gear ratios the gear speeds would be identical and they are not....