Technical Axle ratio calculation

Axle ratio selection? I’m running a programable lock up converter 4 speed overdrive automatic. 3.06 first, 1.63 second, 1.0 third, .70 fourth. Torque curve is flat and pretty consistent from 2800-3800, probably prefer to cruise at 65 in the 2400. I know how to calculate gear and speed. My question is what do I use as a calculation point for good street performance. The second gear speed? Third gear speed or do I calculate cruise speed even though it won’t be highway driven extensively.



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Overall low gear ratio of around 10 is one way to look at it. With the 3.06 first gear, this usually isn't an issue with the 700.

If you're going drag racing, you'd probably want to select rear gears that let you go across the finish line at the RPM that is just past peak HP, in 3rd gear.

Calculations will only get you so far...you eventually have to pick a gear ratio, and see how you like it. I've done a lot of playing around with gears in a couple different vehicles I've owned, and my preference even changes with time, for each one. I really like the 3.89s in my Chevy II, it goes fast and quick at the drag strip, and with the GV overdrive behind the TH400, highway driving is great, and I do a lot of that. I've had everything from 2.75 to 4.11 gears in the car.

 

I am with Jim! And with a lot of thought a 3.89 is what i'm going with myself .
Best to you Mark

 

Have to agree with Jim.
It really comes down to whatever feels right in the car for YOU is the right combination.

Someone else might come to a very different conclusion, and they would be right too.

 

Easy, buy a quickchange and play around with gears !

 

My 1st gear in my M20 was a 2.56 until I broke it, upgraded to newer gears and is now a 2.52. I run a 3.89 rear which is a good compromise in a #3500 car.

 

Did I miss something?What engine is this I have a 4.3 v6 with the same trans. 3:43 works good. Is this a 4 cylinder?

 

Programable? What's that?

 

Tire height too, right?

 

65 mph at 2400 with the OD ratio of your trans and the diameter of your tire factored in = gear ratio in the rear axle You are just looking for something to needlessly worry about with the rest of it.
This chart is plug and play for most things you try to figure out when it comes to rpm, tire size and gear ratio. http://www.wallaceracing.com/calc-gear-tire-rpm-mph.php