Atlas Ratio Questions

[01TJ-Blues]

Hey guys. I’m trying to figure out what Atlas ratio I need for my 32RH. Per @mrblaine there is no difference between the 3.8:1 and the 4.3:1 with the 32RH auto. Per AA they recommend the 3.8:1 but if there isn’t a difference then why not the 4.3:1 or even the 5:1 for if later I sell or change it up? I’m looking for lower gearing than the stock 231 with 35s and 4.56 gearing on a 4.0 with a 32RH. Based on @Alex01 the 5:1 is awesome but not sure how to convert than experience into the 32RH if that makes sense.

If anyone has experience with the 32RH and these ratios it would be appreciated for some input.


Thanks in advance.

 

[Alex01]

With a manual, the 5:1 is amazing because the need to "dance" with the brake and clutch is basically nonexistent. This is because the crawl ratio is increased so much that it's very difficult to stall. Since the manual and auto wheel differently, I like to think of it as push vs pull (YOU telling the jeep to go up a rock vs the JEEP telling you it's going up a rock), the need for a higher crawl ratio isn't as important since stalling isn't an issue.

Here are the numbers though if you're interested....

Looking at them your top speed would be greater with the 3.8:1 (duh) vs the 5:1

**For comparison sake
NV3550 w/4.88 w/ 5:1 - Top speed 16mph @ 3000 rpm 5th gear

32rh w/4.56 w/3.8:1 - Top speed 18mph in 3rd gear @ 3000 RPM

32rh w/4.56 w/5:1 - Top speed 14 mph @ 3,000RPM

32rh w/4.56 w/2.73 (np231) - Top speed 25 mph @ 3,000RPM

My guess is AA recommends the 3.8 on the 32RH because it allows for a higher top speed while still having the advantages of a lower geared box than the NP231. The 5:1 would likely be too slow for the 32rh especially if you wheel in conditions where wheel speed is nessary.

 

[mrblaine]

Hey guys. I’m trying to figure out what Atlas ratio I need for my 32RH. Per @mrblaine there is no difference between the 3.8:1 and the 4.3:1 with the 32RH auto. Per AA they recommend the 3.8:1 but if there isn’t a difference then why not the 4.3:1 or even the 5:1 for if later I sell or change it up? I’m looking for lower gearing than the stock 231 with 35s and 4.56 gearing on a 4.0 with a 32RH. Based on @Alex01 the 5:1 is awesome but not sure how to convert than experience into the 32RH if that makes sense.

If anyone has experience with the 32RH and these ratios it would be appreciated for some input.


Thanks in advance.

You could make the 3.0 work very easily. Doesn't make a lot of sense to spend all that and only get slightly better than the stock 231 though. That leaves the 3.8 and 4.3 as tolerable options. They will give you a good balance of crawl and reasonable top speed in 4low and drive of around 18-20ish if you need to zip up to the next obstacle on good terrain.

Having played with Rubi-crawler some, the OD makes a big difference if you get too low in the case.

 

[01TJ-Blues]

You could make the 3.0 work very easily. Doesn't make a lot of sense to spend all that and only get slightly better than the stock 231 though. That leaves the 3.8 and 4.3 as tolerable options. They will give you a good balance of crawl and reasonable top speed in 4low and drive of around 18-20ish if you need to zip up to the next obstacle on good terrain.

Having played with Rubi-crawler some, the OD makes a big difference if you get too low in the case.

I was leaning towards the 4.3:1 as I also think it’s a nice balance for me. The Rubicrawler would be cool but that’s a transmission swap and I think the 32RH is a better transmission. Overdrive would be nice though.

 

[01TJ-Blues]

With a manual, the 5:1 is amazing because the need to "dance" with the brake and clutch is basically nonexistent. This is because the crawl ratio is increased so much that it's very difficult to stall. Since the manual and auto wheel differently, I like to think of it as push vs pull (YOU telling the jeep to go up a rock vs the JEEP telling you it's going up a rock), the need for a higher crawl ratio isn't as important since stalling isn't an issue.

Here are the numbers though if you're interested....

Looking at them your top speed would be greater with the 3.8:1 (duh) vs the 5:1

**For comparison sake
NV3550 w/4.88 w/ 5:1 - Top speed 16mph @ 3000 rpm 5th gear
View attachment 285560

32rh w/4.56 w/3.8:1 - Top speed 18mph in 3rd gear @ 3000 RPM
View attachment 285546
32rh w/4.56 w/5:1 - Top speed 14 mph @ 3,000RPM
View attachment 285559
32rh w/4.56 w/2.73 (np231) - Top speed 25 mph @ 3,000RPM
View attachment 285561

My guess is AA recommends the 3.8 on the 32RH because it allows for a higher top speed while still having the advantages of a lower geared box than the NP231. The 5:1 would likely be too slow for the 32rh especially if you wheel in conditions where wheel speed is nessary.

Where did you get these charts? This is good stuff. The 3.8 looks like about what I’m after but curious what the 4.3 looks like as well. The 231 is definitely too high for me I feel.

 

[Alex01]

Where did you get these charts? This is good stuff. The 3.8 looks like about what I’m after but curious what the 4.3 looks like as well. The 231 is definitely too high for me I feel.

It was from grimmjeeper.

http://www.grimmjeeper.com/gears.html
I was also thinking you could put your np231 in low and lock it in second. Doing that would more or less simulate the atlas in 3rd between obstacles. If its too slow you know the 3.8 is the way to go. If it's just right the 4.3 is a great choice.

4.3

 

[Jerry Bransford]

Keep in mind automatic transmissions don't have a fixed 1st gear ratio. They have an infinitely low 1st gear ratio and an infinitely high crawl ratio. That's why you don't need as low of a tcase ratio with an automatic as you do with a manual transmission. All of this due to the magic of the automatic's torque converter.

 

[Locrwln]

Years ago, my buddy and built his YJ, 4.0, 32rh, and atlas 4.3. It had Wagoneer Dana 44’s front and rear with 4.88’s and 36” swampers. It was a great combo for rockcrawling the ‘con/fordyce/moab and snowwheeling in the Sierras. I’d go with the 4.3.

Jack

 

[01TJ-Blues]

Thanks for all the insight guys, much appreciated.