Road Runner Nest

Anyone have ideas on a nice gear ratio for a 72' Roadrunner 340c.i. 4-Barrel 727 Automatic? Right now I have 2.76 Highway gears. Although, they are nice and save on gas, I would like to be able to "take-off" the line faster rather than building up my acceleration slowly. I was thinking along the lines of a lower ratio such as 3.55 or lower.


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-Tyler

Nice ride and welcome to the nest! I think 3.23s would be the next step up - still good gas mileage but a little better take off. The 3.55s I think would be a good compromise between mileage and acceleration. You running the standard 8 3/4?

I have some 3.55 sure-grip gears I'll trade you for a 3.23 sure-grip!

I wish I had either one

I had 3.23s in mine (When the powerplant was a mild 383) and 727. I upgraded those to 3.91s. Lots more oomph, but winds a little bit to high to make it a real long-tripper.

There are some gear ratio / rpm calculators out there. That way you can get an idea of how many RPMs you'll be turning at cruising speed.

http://www.csgnetwork.com/multirpmcalc.html

Great link. This will help alot!

You can also change first gear in the transmission by installing a four gear planetary set found in most motorhome trannys.

Thanks for the reply. Im looking for a planetary system right now. haha

To correctly do a drivetrain for performance. You should profile it from the flywheel back.

There are several ways to improve take off time.

Suspension

Transmission

Differential

Remember if you increase the ratio ie 2.76 2.71 2.79 to a 3.23 3.55 etc

the higher the number the higher the rpm will need to be to sustain speed if you are looking to spin tires

then a higher ratio usually for quarter mile launching however if you contact a drivetrain specialist they do

lower ratio sure grip systems ie 2.7 etc etc ford 9 inches will bolt up and they come in those ratios for the

budget minded builder or you can contract strange or dts and they will make you a dana with sure grip and

ratio of your choice for about 2 thousand dollars but i would choose a mid range ratio and go with a 6 speed

transmission

bruce wrote:I have some 3.55 sure-grip gears I'll trade you for a 3.23 sure-grip!

i have 391 gear id trade you

beep beep guy wrote:

bruce wrote:I have some 3.55 sure-grip gears I'll trade you for a 3.23 sure-grip!

i have 391 gear id trade you

I'm looking to go lower (numerically) not higher! The engine in my car is screamin' when I take it out on the highway...

Guess I won't be looking for 3.55's haha. Wouldn't want to beat my engine too bad =) 3.23's sound solid to me

bruce wrote:

beep beep guy wrote:

bruce wrote:I have some 3.55 sure-grip gears I'll trade you for a 3.23 sure-grip!

i have 391 gear id trade you

I'm looking to go lower (numerically) not higher! The engine in my car is screamin' when I take it out on the highway...

If you think 3.55s are rough on the highway, try the 4.10s that came with the super track pack! DAMHIK

beepbeepTyler wrote:Guess I won't be looking for 3.55's haha. Wouldn't want to beat my engine too bad =) 3.23's sound solid to me

Depends on your combo too--mine is a 451 6bbl with reworked heads and a healthy cam. It's gonna turn different revs than your 318... just a bit of difference.

Bruce, Im sure it will hahah

and its a 340 (in process of being a 416 stroker) Don't low ball me haha