Rear Gears

[Terry Hauck]

I have a 69 Roadrunner with a bit above stock 440, a 4-speed, and a 509 cam. I have to slip the clutch to get it going with the stock 3.23 gears. What ratio would you guys run, 3.73 or 3.91??

 

[69hemibeep]

If you want to run down the highway at all 3.55, its about 300 RPM more at highway speed and 300 more for each gear set lower. How tall are the rear tires ? I'm around 3000 RPM at 70 with 3.54s

 

[Russ69Runner]

Have to pedal mine to take off in first gear. 383 four speed. Just get use to it I guess.

 

[Terry Hauck]

If you want to run down the highway at all 3.55, its about 300 RPM more at highway speed and 300 more for each gear set lower. How tall are the rear tires ? I'm around 3000 RPM at 70 with 3.54s

28 inch

 

[69hemibeep]

https://www.reillymotorsports.com/speed-tire-rpm-calculator

 

[Terry Hauck]

https://www.reillymotorsports.com/speed-tire-rpm-calculator

That is really cool, thanks. Looks like about 70 mph at 3200 rpm with the 3.91 gears. I rarely, if ever, drive on the freeway with this car, so 3.91s might be a lot of fun around town. Thanks again

 

[mr4speed]

Try 430s you be top dog in your area a little less mpg but lots of fun

 

[V.R.D]

I run a 30-in tire with a 355 gear at 70 mph on cruise control at 3000 RPM. there's a calculator for this so best to use that.

 

[V.R.D]

https://auto.howstuffworks.com/auto...wing/maneuvers/gear-ratio-tire-size-chart.htm. check out this chart

 

[Terry Hauck]

https://auto.howstuffworks.com/auto...wing/maneuvers/gear-ratio-tire-size-chart.htm. check out this chart

Thanks

 

[V.R.D]

Your welcome sir