transmission choice opinions

[LongHorn]

with the peek torque on the 304 being about at 2500 RPM I can see where this is a good chart for you. I am thinking at this moment that with the 4.2 the prime RPM range may be a bit lower. Closer to 2K. This may be some sad rationalization to justify my 3.54 axles but this is my opinion for the moment at least.

I don't think your far off IO, when I ran a "Four Deuce" with a T-18A.
I ran 3.92 gears with 33" BFG M/T's.

 

[Old Dog]

The thing with the chart is, it doesn't allways work out as planed. For instance I run "33" inch tires, they measure more like 31 or 32 at best. But looking at the chart, it says I'm running more like 30's. (2900-3000 rpm). But hey thats ok cause my 350 is just starting to purr than.
Has anyone else tryed using the chart and if so how close was it for you?

The old math way is... RPM = MPH X gear ratio X 336 divided by tire dia.

 

[LongHorn]

The thing with the chart is, it doesn't allways work out as planed. For instance I run "33" inch tires, they measure more like 31 or 32 at best. But looking at the chart, it says I'm running more like 30's. (2900-3000 rpm). But hey thats ok cause my 350 is just starting to purr than.
Has anyone else tryed using the chart and if so how close was it for you?

The old math way is... RPM = MPH X gear ratio X 336 divided by tire dia.

Hey Dog,
Have you tried measuring from the center of your hub to the ground, then take that (number X 2)= Real Tire Diameter, not advertised diameter.

 

[Old Dog]

Horn, thats where I came up with 31-32" depending on air pressure,
at 12 lbs They are more like 26's

Back to the chart or formula I think me haveing an auto (torque converter)screws with the numbers some. Thats why I was wondering how well it worked for other guys.

 

[LongHorn]

Horn, thats where I came up with 31-32" depending on air pressure,
at 12 lbs They are more like 26's

Back to the chart or formula I think me haveing an auto (torque converter)screws with the numbers some. Thats why I was wondering how well it worked for other guys.

Rodger that, over.

 

[LongHorn]

Horn, thats where I came up with 31-32" depending on air pressure,
at 12 lbs They are more like 26's

Back to the chart or formula I think me haveing an auto (torque converter)screws with the numbers some. Thats why I was wondering how well it worked for other guys.

Airing downs two fold benefit;
Better ride & lower final drive ratio for off road.

 

[BusaDave9]

Yes, it's true that the tire size isn't always what the manufacturer says it is. The chart shows your RPM at 65 MPH. The equation to calculate RPM is this:

MPH x Gear ratio x 336

Tire Diameter​

This is meant as a guide to help decide on a ring and pinion gear ratio. It works whether you are building a rock crawler or a highway cruiser.


Anything in the green is from 2700 rpm to 3050 rpm. That is close to stock gearing. If you are building a rock crawler you may want to go into the red area. Not only will the intended use of your jeep help decide what rpm you want to be at on the freeway but also other factors such as your tranny. The chart assumes you are in a gear that is 1 to 1. If you have an Overdrive you could get lower gears. If you have an automatic it can handle higher gearing because the torque converter can help you get started or during rock crawling.

 

[Out of my mind CJ5]

thanks for the link it helped clear up some questions i had, it is looking like i might be looking for a chevy front axle now as some already have the high steer knuckles on them and they will closer match my rear axle width, does anyone have advice on what year trucks i should be looking at and what type, has to be 8 lug

hey guys sorry to hange the topic but still looking for front axle advice if anyone has any?

 

[LongHorn]

hey guys sorry to hange the topic but still looking for front axle advice if anyone has any?

I run a 86' Chevy CUCV 1028 front axle with high steer arms.
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