I have an f350 that I'm slowly converting to an F100. I'm building a 333 stroker Y block, I have a T5 tranny that I'm going to have John modify for me. I had a nine inch that I got for free that turns out is junk. So, I've been on the hunt for a rear axle. Ideally I was thinking about either a 3.70 final drive, for highway/freeway economy. But a 4.11 sure would be fun around town. So, the only pieces of info that will help you guys are the tire diameters- 30 inches. And the overdrive gear in the T5 is a .79.



With the 4.11 it wood put my RPMs right at about 2500 for 70mph.



What are your opinions on final drive ratio for my application. Will I be happier with a 4.11 for gunning an occasional street light. Or should I go with the taller gears for economy sake?

Heber City, UT (15 mins outside of Park City- basically it's in the mountains)

55 Effie

I had a 4:11, 3sp in my 57 Ford and while it was fun around town 70mph was out of the question. Did the T5 swap and the car is just a joy to drive now. Almost went with a toploader. Glad I didn't.

Dan      Kingman Az.      86409

Come on now. I know you're not building a stroker for economy.

But honestly, I think the 4.11 will be just right. And, in reality, the shorter gear may turn out to be the more economical gear. If you're below the power band of the engine with the 3.70, then your performance and economy will suffer.

I currently have a 3.70 with .63 overdrive and 27.4" tires and I'm under 2000rpm @ 70. It's too tall for mine. I'm probably going to end up using a 4.30.


Lawrenceville, GA

4:11 for sure. I'm sure you will be sorry if anything higher and your engine will appreciate it.

Ol'ford nutCentral Iowa

56 Vic w/292 & 4 spd.

That just made me laugh! Thanks Charlie!

Heber City, UT (15 mins outside of Park City- basically it's in the mountains)

55 Effie

Um, you want economy in an F350? Yeah! I want the same in my F-600!!!





All kidd'n aside, I AM actually trying to the same thing with my F-600!



My trans will have a 0.71:1 OD and a "lock-up" torque converter.....and with the 5.83 final rear ratio I expect about 2100 RPM on the freeway at 60mph. (I have 40" tires!! )



There's no reason for you not to expect the "good" mileage with "tall" gears!



I don't know what the "empty" mileage would be but it you "keep your foot out of it", it shouldn't be "bad"....... PLUS you will have somewhat low gears for that "hole-shot"!





Make sure you do a video so we can all see and hear!!











Cheers,





Rick










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1955 F-600/272/E4OD// Disclaimer: No animals were injured while test driving my F-600 except the ones I ran over intentionally!

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