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Discussion Starter #1
What effect on E.T. would the following have if we currently have 2.56 ?


1) 3.73 ?

2) 4.56 let's assume the engine CAN turn whatever rpm it turns out to be in the lights.


a) All other things being equal

b) General/ballpark.
 

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Discussion Starter #2
NOTE: The forum said it didn't post (or so i thought....) which is why there are multiple postings of the same topic. Sorry!
 

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The Forum is having some tech glitches... I removed 5 of your extra duplicate threads
 

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A standard transmission 2.56 first gear would be great. But if you referring to rear axle not so much. The 3.73 is a good rear gear with a low 1st gear.
Torque multiplication with automatic and converter foot brake, change to line lock will make the biggest difference.
Actually your question is too vague.......
 

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Faster 60 foot times, if you can keep it hooked up and not blowing the tires off it at the line.
As far as et it depends on so much more.
Where is the power band? Where will the new gears put the rpm in the power band in each transmission gear before it shifts. what are the transmission shift points(automatic), Will the gearing say 456 or the 373, when trans shifts into 3rd, be at the low end of the powerband through the lights, or outside/past the powerband.
When going through the lights you want to be at or near the power peak. to far past it, it'll fall on it's face, to low in the powerband it won't pull strong at the top half of the track.
 

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What car, what weight, what powertrain, what modifications, what is the thing being used for?
 

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Discussion Starter #7 (Edited)
1/2 ton 2WD truck, at least 3600 lbs. (according to the gm tech sheets)

stock, crate 350 with stock cam (so probably 196/196 @ .050 lift, real tame) i can look it up the exact specs if we need to.

TH-350 trans, 2000 stall converter

P235/75 15 rear tires, but let's assume no spin in either case.

Best e.t. according to digital gauge is 16.8 secs

2) Same as above except stock 4.3 v-6 with "z" series cam, so approx 196/196 ish @.050 lift. i can look up the exact specs if we need to.

Just looking for ballpark estimates on E.T. change, if any.
 

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Discussion Starter #8
P.S.
Eventually, the drivetrain will be used only for race only in another car; i am using the truck as a rolling "test stand."

The car will at, or under 2000 lbs.
 

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Discussion Starter #9
P.P.S.
We're looking at stock-ish engines with stock internals, so we need to keep it under 5000rpm.
 

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You don't get to choose a rear gear ratio.

It chooses you.

Application dictates gear ratio.
for economy, the final gear must provide adequate cruise MPH and RPM for minimal friction and minimal wasted energy.
for 1/4 mile racing, the rear gear ratio is determined by the weight, power and rpm capability of the vehicle, e.g. 3000lbs 500-700rwhp, 27.4" Tall tire, max rpm 6300rpm, the car needs to be able to achieve at least 140mph so the use of a 3.2 to 3.4:1 ratio would be ideal. A 3.73 would not work for that application.
For 1/2 mile or 1-mile racing, a 2.70 or 2.50:1 might be required to get the mph 180 200 etc...
Some engines can spin 9000rpm or more so the gear ratio always needs to adjust to suite the ability of the engine/trans and weight. Some vehicles go up and down in weight frequently (trucks carrying loads) and this too must be factored into the ratio of the differentials and trans.
 
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