Please Explain Gearing (Rear End) - Page 3 - Dodge Charger Forums
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#21 Old 11-12-2012, 08:58 AM
POWERMAN
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Very informative thread..thank you for this!

I know it's not possible..but imagine if folks figured out a way in which one could select what kinda rear axle ratio they wanted at the push of a button?

Just thinking out loud... : p

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#22 Old 11-12-2012, 09:09 AM
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Another thing to remember is that every engine 'likes' a particular rear gear. If you over- gear your engine, you end up with what Hazmat said. If you're crossing the line at the time when your engine is no longer making horsepower (torque X RPM/5252), you aren't gaining anything. Your ideal rear gear will allow you car to be in the power band when it crosses the line. Too long of a gear = not optimum... too short of a gear = not optimum. You want a good balance between.
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#23 Old 11-12-2012, 10:38 AM
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Commercial trucks have 2 speed drive axles. Use it to split the transmissions gears for heavy loads. That's a lot of shifting. Regarding top speed, a lower gear, numerically, does not necessarily mean a faster car. You got to have the horsepower to pull a tall gear. Power needs go up drastically to go fast. 150 might get touched, but not for long!

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#24 Old 11-12-2012, 07:32 PM
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Quote:
Originally Posted by michiganpat View Post
what tranny do you have? 42RE has a .69:1 OD, making your 3.64's an effective 2.51 overall top gear ratio. the NAG1 5 speed has a .83 OD, turning the 3.64 into an effective 3.02 overall top gear

28" tall tires with 3.64's would put 5000 RPM at 138 MPH with a NAG1, and 166mph with a 42RE

the 42RE has a 2.74 first gear, whereas the NAG1 has a 3.59 first gear...so....

a 42RE with a 3.64 has an overall first gear ratio of 9.97:1
a NAG1 with a 2.82 has an overall first gear ratio of 10.12:1
a NAG1 with a 2.65 has an overall first gear ratio of 9.51:1
Nag1 i was talking about on the highway...Not 1/4 It gets to 130 rather quickly but hell im scared to push it pass it not sure if it could or not lol.


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#25 Old 08-13-2013, 09:17 PM
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Quote:
Originally Posted by POWERMAN View Post
Very informative thread..thank you for this!

I know it's not possible..but imagine if folks figured out a way in which one could select what kinda rear axle ratio they wanted at the push of a button?

Just thinking out loud... : p
Rockwell and Eaton make, or used to make, 2 speed axles for heavy duty trucks. Nothing for cars though.

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#26 Old 08-13-2013, 11:03 PM
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the rearend gearing thing can be alittle overwelming, alot of roundy round racers well install quick change rearends for differant length tracks to stay in peak power powerband - rpm. Far as drag racing its all about traction ,to low gears usally ends up with smoking tires, to high of gears slower start with wasting time building rpm. What usally happens with new lower gears is need for bigger tires to get traction back. Many races lost by to much torque and not able to get traction. The combination of the the right gearing to HP getting traction makes a fast car
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#27 Old 08-15-2013, 09:57 AM
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I've always thought the 3.73 was the perfect gear for a street car. Great torque response, and not too bad on the highway. Kind of the best of both worlds. Also 3.42 is a great gear.

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#28 Old 08-15-2013, 11:12 AM
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Quote:
Originally Posted by POWERMAN View Post
Very informative thread..thank you for this!

I know it's not possible..but imagine if folks figured out a way in which one could select what kinda rear axle ratio they wanted at the push of a button?

Just thinking out loud... : p
Closest you can get in a street car is a Gear Vendors Over/Underdrive. Basically a splitter gearbox, mounts to the rear of the trans, you make a custom driveshaft to fit back to the diff. Makes your 5 speed trans a ten speed. Of course, our trans doesnt have an application, cannot imagine the programming required. and they are pricey, at close to 3K a pop, not counting the few hundred for the driveshaft.

Come the day I get moving on the 68 Cougar, I hope to find the cash to strap one behind the C6 trans in that car.

"For a mechanic, you seem to do an excessive amount of thinking."
―C-3PO, to R2-D2

Last edited by GLHS837; 08-15-2013 at 11:24 AM. Reason: For basic math:)
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