# Gear calculator



## Poncho Dan (Jun 30, 2009)

I'm looking for a gear calculator. I want to find out (mostly) what my RPMs will be at 70mph, my normal cruising speed with different diff ratios, and possibly for determining a custom gear set for the T56.

Also, I don't suppose anyone knows the stock 1st-6th ratios offhand?

Thanks.:cheers


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## GM4life (Mar 18, 2007)

First
2.97

Second
2.07

Third
1.43

Fourth
1.00

Fifth
0.84

Sixth
0.57


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## BRZN (Jan 31, 2011)

Check this out:

UtimateGTO.com: Top Speed Calc - Driveline Data 2006


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## LS2 MN6 (Jul 14, 2010)

FWIW, 4th is typically 1-1 on all 6-speed manuals. So even with a custom gearset you might want to keep that.


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## LS2 MN6 (Jul 14, 2010)

BRZN said:


> Check this out:
> 
> UtimateGTO.com: Top Speed Calc - Driveline Data 2006


The problem is even unrestricted the 6th gear would never get to 250 mph (as the calc says). It doesn't have the torque at high RPM's to overcome the drag force on the car.

This is why Corvettes reach top speed in 5th gear. I'd imagine the GTO is the same. Making top speed at 170. 6th MIGHT be able to push that to 180, but I'd have to see it in real life.


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## Poncho Dan (Jun 30, 2009)

LS2 MN6 said:


> FWIW, 4th is typically 1-1


Yes.

I'm looking to have a custom transmission build that mimics the T-10 style I had in my '64GP, a 2.28 1st gear with evenly spaced ratios through 4th, even 5th for this thing, and 6th would be the MPG/"highway" gear. I'm just looking to bring the ratios closer together, make it worth the time to install 3.91's in the back...


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## GM4life (Mar 18, 2007)

Some things to keep in mind. Lower #ratio(higher gear)the stonger the gears will be. Also you don't have to keep 1:1 on the 4th gear you can move it to 5th and have just sixth the overdrive. Some aftermarket trannies like Richmonds are setup that way. Just have to keep in mind if you have to shift or not toward the back end of the track.


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## Poncho Dan (Jun 30, 2009)

We'll see what can be built. I was thinking about fabricating a paddle shift setup, but now I'm wondering if it wouldn't be easier to install a hydraulic clutch override right on the shifter, similar to a motorcycle clutch lever. That way you could retain the pedal, but be able to shift quick like a paddle setup or jamming straight-cut gears.

I know I'm getting towards the fringe with this stuff, but I figure, go big or go home. Try something different...


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## GM4life (Mar 18, 2007)

I would rather have a sequential gear box than anything else like a Holinger gear box. Adding complexity adds more things that can go wrong. Flappy paddle trannies are manumatic trannies that have twin disc no torque converter.


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## AlaGreyGoat (Jul 6, 2006)

I, also would like have a sequential gear box, BUT the $24-28 Grand
price is a little inhibitive at this time.

Larry


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## GM4life (Mar 18, 2007)

AlaGreyGoat said:


> I, also would like have a sequential gear box, *BUT the $24-28 Grand
> price is a little inhibitive at this time*.
> 
> Larry


I'm with you.


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## Poncho Dan (Jun 30, 2009)

I'd bet an extra clutch master actuated by either a solenoid or manually at the shifter would be a heck of a lot cheaper than a sequential box. Shouldn't be all that complicated either, in theory.


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## danfigg (Sep 27, 2009)

*re*

why not mimic the A6 tranny ratio's from the G8 in a 6 speed tranny. Those car run 13's with 2.90 ratio's. Steep first gear to get the car out of the hole would be nice---danfigg 

6L80
4.03 x 2.92 = 11.76 1st
2.36 x 2.92 = 6.89 2nd
1.53 x 2.92 = 4.46 3rd

Turbo400
2.48 x 4.56 = 11.30 1st
1.48 x 4.56 = 6.74 2nd 
1.00 x 4.56 = 4.56 3rd


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## AlaGreyGoat (Jul 6, 2006)

Normally, in a manual trans, the lower the low gear, the weaker
the trans is. Rearend are usually stronger than transmissions,
so having a higher low gear in the trans and a lower rearend gear
is more suited. The down side is you need overdrive gearing for good
hiway crusin'. OD gearing is also weak in a manual
trans.

Larry


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## GM4life (Mar 18, 2007)

danfigg said:


> why not mimic the A6 tranny ratio's from the G8 in a 6 speed tranny. Those car run 13's with 2.90 ratio's. Steep first gear to get the car out of the hole would be nice---danfigg
> 
> 6L80
> 4.03 x 2.92 = 11.76 1st
> ...


Keep in mind that steep first gear makes up for that high geared rear end ratio. That tranny has a different purpose than the T-56 does.


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