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FINALLY - C7 3.90 and 4.10 Differential Gear Sets

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FINALLY - C7 3.90 and 4.10 Differential Gear Sets

 
Old 02-15-2019, 07:57 AM
  #21  
Pumba
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With the M7 transmission you do not need to recalibrate the speedometer.
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Old 02-16-2019, 02:14 PM
  #22  
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Originally Posted by Pumba View Post
With the M7 transmission you do not need to recalibrate the speedometer.
However your speedometer will be reading slightly higher than your actual speed.
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Old 02-16-2019, 09:45 PM
  #23  
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Originally Posted by Bubbletop409 View Post
,

The point being competition gear sets are not recommended for street use, and visa versa, So again what grade of steel are these made of and for what venue were they designed? Street or true competition? And as a side note these are gears for the rear differential, not the transmission as some are assuming.
i think you are confusing these with drag only gear sets which are made if a softer alloy which makes them less brittle and allows the gears to absorb the shock of a launch. The downside of these gears is that they wear quicker. These gears donít appear to be drag only gears.
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Old 02-16-2019, 09:56 PM
  #24  
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Originally Posted by Pumba View Post
With the M7 transmission you do not need to recalibrate the speedometer.
How will it read the correct gear ratio without recalibrating the ECM?
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Old 02-16-2019, 10:28 PM
  #25  
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Originally Posted by Bubbletop409 View Post
However your speedometer will be reading slightly higher than your actual speed.
Modern vehicles use wheel speed sensors. The only thing that will change your speedometer is tire height. Since the C5 for sure, not sure about the C4.

Originally Posted by phantom1 View Post
How will it read the correct gear ratio without recalibrating the ECM?
Gear ratios are pre-programmed into the engine and transmission calibrations and the gear position indicator is set and can be learned with a GM tool (but isn't needed).
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Old 02-18-2019, 08:30 AM
  #26  
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Subscribed.
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Old 02-18-2019, 10:09 AM
  #27  
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Iím interested and n the 3.90 but why different recommendations between the stingray and GS?
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Old 02-18-2019, 01:31 PM
  #28  
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Originally Posted by Higgs Boson View Post
Modern vehicles use wheel speed sensors. The only thing that will change your speedometer is tire height..
Then why is it that only the M7 equipped cars automatically adjust?
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Old 02-18-2019, 01:37 PM
  #29  
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Originally Posted by 383vett View Post
i think you are confusing these with drag only gear sets which are made if a softer alloy which makes them less brittle and allows the gears to absorb the shock of a launch. The downside of these gears is that they wear quicker. These gears donít appear to be drag only gears.
I'm not confusing, I know well the difference, hence the question. I guess the better question would then be why would one desire them for street use?
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Old 02-18-2019, 04:17 PM
  #30  
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Originally Posted by devnull View Post
HECK YEAH DUDE!

Been lurking this topic since 2015... THANK YOU!!!
same here!
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Old 02-19-2019, 10:59 AM
  #31  
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Originally Posted by Bubbletop409 View Post
Then why is it that only the M7 equipped cars automatically adjust?
you adjust the autos so the shift speeds are still correct.
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Old 02-19-2019, 06:58 PM
  #32  
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I'm thinking that as low as it is I can start out in 2nd without clutch burn.Thats a plus.
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Old 02-19-2019, 07:44 PM
  #33  
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Out of curiosity, Lets say I am trapping 140-141 consistently in the 1/4 with my M7 Stingray. Is there any kind of guess what this would raise my trap speed to with a 4.10 set? Purely speculative, not looking for an exact scientific number. Just trying to gauge the expected performance gain from going to these gears.

And any estimate on labour time? My car is going into a shop for a month and will already be on a lift with the motor out....
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Old 02-20-2019, 01:40 PM
  #34  
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Originally Posted by blue_bomber697 View Post
Out of curiosity, Lets say I am trapping 140-141 consistently in the 1/4 with my M7 Stingray. Is there any kind of guess what this would raise my trap speed to with a 4.10 set? Purely speculative, not looking for an exact scientific number. Just trying to gauge the expected performance gain from going to these gears.

And any estimate on labour time? My car is going into a shop for a month and will already be on a lift with the motor out....
It all depends on setup and power curve. With most cars you want to shift several hundred rpm above peak hp and go through traps above as well. This will yield the best et and mph provided traction and that your car can handle it and run stable at those rpms.
So, you can do a comparison with your current gears vs. 4.10 gears on a spreadsheet based off the data from a dyno graph to see which one will work better.
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Old 02-20-2019, 01:50 PM
  #35  
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Originally Posted by robz View Post
It all depends on setup and power curve. With most cars you want to shift several hundred rpm above peak hp and go through traps above as well. This will yield the best et and mph provided traction and that your car can handle it and run stable at those rpms.
So, you can do a comparison with your current gears vs. 4.10 gears on a spreadsheet based off the data from a dyno graph to see which one will work better.
My issue is though, if I were to go to 4.10 gears, that limits the top of 4th to ~145mph @ 7200rpm (my redline) and if my trap were to increased too much, I would run into the issue of hitting redline right before the 1/4 mile traps. I'll give RPM a call and see what they think. 3.92 might be the safer route to go?
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Old 02-20-2019, 03:45 PM
  #36  
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Talked with RPM today and they said Trap speed shouldn't change too much, might pick up in the 1/8th but lose on the back half for instance, but we really won't know till some cars get out there and try them out. But the gear sets are $850 and about 15 hours of labor to install for all of you interested.
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Old 03-14-2019, 05:46 PM
  #37  
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Originally Posted by Higgs Boson View Post
Modern vehicles use wheel speed sensors. The only thing that will change your speedometer is tire height. Since the C5 for sure, not sure about the C4.



Gear ratios are pre-programmed into the engine and transmission calibrations and the gear position indicator is set and can be learned with a GM tool (but isn't needed).
I have 3.90 gears in my C7 M7 and it doesn't seem like the ECM is learning the new gears. I'm about 90% sure it's 5-7 mph higher. I've made three 20 mile trips in the process of breaking-in the gears. Is there a certain amount of miles it needs, to learn?

Last edited by phantom1; 03-14-2019 at 05:47 PM.
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Old 03-14-2019, 06:56 PM
  #38  
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Originally Posted by phantom1 View Post
I have 3.90 gears in my C7 M7 and it doesn't seem like the ECM is learning the new gears. I'm about 90% sure it's 5-7 mph higher. I've made three 20 mile trips in the process of breaking-in the gears. Is there a certain amount of miles it needs, to learn?
no there should be no learning needed. unless something changed with the C7, I don't think anyone has been swapping gears in manuals until now.....maybe I am wrong about it.
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Old 03-14-2019, 08:13 PM
  #39  
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Originally Posted by Higgs Boson View Post
no there should be no learning needed. unless something changed with the C7, I don't think anyone has been swapping gears in manuals until now.....maybe I am wrong about it.
There wasn't anybody around when I took the car out today. I'll coast with someone side by side and compare mph asap.

Thanks

Last edited by phantom1; 03-14-2019 at 08:14 PM.
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Old 03-14-2019, 09:02 PM
  #40  
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Originally Posted by phantom1 View Post
There wasn't anybody around when I took the car out today. I'll coast with someone side by side and compare mph asap.

Thanks
Should look into getting a Dragy, or borrowing a Dragy/Vbox from someone else who has one. That will tell you for sure and then you can also compare performance data.
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