Crawl Ratio Calculator or Speed

I'm sure others who are more experienced than I already know how to calculate this, but still I thought it was kinda neat and easy.

http://www.4lo.com/calc/gearratio.htm

I have an Atlas II T-case and didn't really know what gear ratio I had so I did a search and there apparently three available.

The NV4500 also had two options. One made before 92 with a ratio in the sixes and the later with 5.61 so I'm using the later ratio.

Three options of the T-case

3.03 resulting in a crawl ratio of 77.51
3.77 - CR of 96.44
4.33 - CR of 110.77

All of these were with an RPM of 1000 but I couldn't really understand how the RPM would affect it. Unless of coure the RPM option would only be needed to calculate your speed based on the gear ratio and tire size. Come to think of it I'd bet that's the only reason it's there, but

 

For comparison sake I input the numbers for Nixon

3.73 gears 3.10 1st gear in the T-14 Tranny and 2.42 ratio in the D-18 T-case equates to a 27.98 crawl ratio.

 

John they also have a 5:1 case.

 

I wish I knew how to tell which one I had. Unless I'm mistaken there are some numbers on the back of mine, but they don't agree with any of the three I posted or the one you posted...maybe I'll check again tonight.

 

Kinda cool aint it?

 

Tire diameter and RPM don't affect crawl ratio.

 

I am in the mid to high 50s IIRC. No need for an online calculator, if you know your ratios then you can use a normal calculator.

 

Uh huh. My truck is 3.0 * 2.03 * 3.54 = 21.6

 

now figure out an auto, the convertor doubles the ratio mine is ( gear on gear ) 4L60=3.06/NP205=1.96/rockwell axles=6.72 is 42 to 1, but if you figure the T/C it will all most doulbe the crawl so i am in the 75/80 to 1 range, jason.

 

T18a + D20 + 4.56 gears=58:1

 

84.7:1 here. You guys with crawl ratios in the 20s don't know what you're missing. (At least for rocks)

John, how did you end up buying an Atlas II and not knowing the ratio?

 

37.21 here. Not too bad.

 

He's a bum and bought the Jeep with the Atlas already installed!!!

R)

 

Yep, it's kinda boring too. The only thing I've installed on this jeep are some fancy schmancy speaker enclosures.

 

(SM242 @ 7) * (D18 @ 2.42) * (4.11 rear) = 69.62 Works very well.

Finally. First trail ride this year and first with twin stick conversion yesterday,
10+ hours in low range.

 

7.05 first in the tranny, 2.46 in the D-18 and 4.27 in the axles = 74:1. I think that should be plenty low for what I am doing and If not then just apply more right foot until something breaks... haha..

BUBBA :v6:

 

Well, you could always use that calculator backwards. Put it in low range, and note the RPM for a particular MPH and you should be able to figure out ratio is closest. Of course it requires an accurate speedo and tach.