Question about gear ratio in a TJ Rubicon automatic with Rubicrawler

deadbeat son said:
I'm confused by this. Why would you want a RubiCrawler for a 231 but not a 241OR? It seems like it would offer a lot more flexibility with the 241OR.

231 / RubiCrawler Ratios:
  • TC H / RC H - 1:1
  • TC H / RC L - 2.7:1
  • TC L / RC H - 2.7:1
  • TC L / RC L - 7.29:1
241OR / RubiCrawler Ratios:
  • TC H / RC H - 1:1
  • TC H / RC L - 2.7:1
  • TC L / RC H - 4:1
  • TC L / RC L - 10.84:1
Based on that, it seems like the 241 OR with the RC would be a really sweet setup!
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I don’t disagree as it definitely would be. Me personally, I’m in the same boat as others when I want a little more wheel speed in 4LO. With the 231 in other Jeeps I always felt 4LO was good if you needed to get on it, but a little more depth would have been nice. A Rubi crawler would have tied things off nicely, which is why I wanted to go that route originally.
 
deadbeat son said:
You're welcome. People can tell you that something is a bad idea all day long, but sometimes it helps to understand why.



I'm confused by this. Why would you want a RubiCrawler for a 231 but not a 241OR? It seems like it would offer a lot more flexibility with the 241OR.

231 / RubiCrawler Ratios:
  • TC H / RC H - 1:1
  • TC H / RC L - 2.7:1
  • TC L / RC H - 2.7:1
  • TC L / RC L - 7.29:1
241OR / RubiCrawler Ratios:
  • TC H / RC H - 1:1
  • TC H / RC L - 2.7:1
  • TC L / RC H - 4:1
  • TC L / RC L - 10.84:1
Based on that, it seems like the 241 OR with the RC would be a really sweet setup!
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It’s cool to talk about a 10.8:1 low, low range, but it’s not really useful. 4:1 is incredibly slow. If you’ve not experienced that, you really should.

To me, a perfect combo would be something around 2:1 and 3:1 so combined, they are 6:1. I’ve priced out an atlas with 2:1 and 2.73 to one and it’s very expensive…like 9k. That’s when I started thinking about the rubicrawler and an NP205 at 1.96:1. That would give me 2.73:1 in the under drive. 1.96:1 in the Tcase, and 5.35:1 with both of them engaged. I can also set the 205 up with twin sticks to allow for front digs and 2wd low. Finally…I believe the NP205 is shorter than the nv241or, so I would gain some drive shaft length.
 
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Mike_H said:
It’s cool to talk about a 10.8:1 low, low range, but it’s not really useful. 4:1 is incredibly slow. If you’ve not experienced that, you really should.

To me, a perfect combo would be something around 2:1 and 3:1 so combined, they are 6:1. I’ve priced out an atlas with 2:1 and 2.73 to one and it’s very expensive…like 9k. That’s when I started thinking about the rubicrawler and an NP205 at 1.96:1. That would give me 2.73:1 in the under drive. 1.96:1 in the Tcase, and 5.35:1 with both of them engaged. I can also set the 205 up with twin sticks to allow for front digs and 2wd low.
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Sure, the 10.8:1 is incredibly slow, but the RC/241OR combo gives you the option of both 2.71:1 and 4:1 in addition to that ridiculously low ratio. However, with the RC/231, you only get 2.71:1 or 7.29:1, which is also really slow.
 
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deadbeat son said:
Sure, the 10.8:1 is incredibly slow, but the RC/241OR combo gives you the option of both 2.71:1 and 4:1 in addition to that ridiculously low ratio. However, with the RC/231, you only get 2.71:1 or 7.29:1, which is also really slow.
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Ahhhh, I see what you’re saying now. Basically you could run it with the 2.7:1 ratio and you’ve basically got the low range of a 231, in addition to the 4:1.

Which now means that buying one is way more on the table than I thought 🥲
 
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Jamison C said:
Ahhhh, I see what you’re saying now. Basically you could run it with the 2.7:1 ratio and you’ve basically got the low range of a 231, in addition to the 4:1.
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Yes, exactly! That's why I listed out all of the combinations in my first post, I tried to make that point. I just must not have communicated it well. The RC with a Rubi's 241OR gives you the best of both worlds. You wouldn't get that flexibility with a 231.
 
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Nobody mentions that 10.8:1 will grenade front axle u-joints if a tire binds and power continues to be applied. That said, the single biggest value of a Rubicrawler is when paired with the 241, to give you a 2.72:1 or 4:1 option in 4 low. If you don't need both of those, it's not worth the money.
 
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deadbeat son said:
Sure, the 10.8:1 is incredibly slow, but the RC/241OR combo gives you the option of both 2.71:1 and 4:1 in addition to that ridiculously low ratio. However, with the RC/231, you only get 2.71:1 or 7.29:1, which is also really slow.
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You also get 2nd low.
 
deadbeat son said:
Sure, the 10.8:1 is incredibly slow, but the RC/241OR combo gives you the option of both 2.71:1 and 4:1 in addition to that ridiculously low ratio. However, with the RC/231, you only get 2.71:1 or 7.29:1, which is also really slow.
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Valid point. I believe I posted earlier that the best thing about putting the rubi in a Rubi would be picking up the additional range between 1:1 and 4:1.

I do think that in an auto the 10.8 would likely be pretty useless - but I have no personal experience. I’ve heard a few people who have the rubicrawler indicate such, even about the 7:1.

But, the 10.8 may work great behind a five speed.
 
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NashvilleTJ said:
Valid point. I believe I posted earlier that the best thing about putting the rubi in a Rubi would be picking up the additional range between 1:1 and 4:1.

I do think that in an auto the 10.8 would likely be pretty useless - but I have no personal experience. I’ve heard a few people who have the rubicrawler indicate such, even about the 7:1.

But, the 10.8 may work great behind a five speed.
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Yes you did, but that suggestion seems to be totally overlooked by a number of other people. 🤷‍♂️

In regards to your comment about people reporting the 7:1 as being useless, that's why I can't figure out why anyone would want the RC with a 231 but not the 241OR. There is zero flexibility with the 231/RC setup. You either get 4H, stock 2.71:1, or 7:1.
 
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deadbeat son said:
Yes you did, but that suggestion seems to be totally overlooked by a number of other people. 🤷‍♂️

In regards to your comment about people reporting the 7:1 as being useless, that's why I can't figure out why anyone would want the RC with a 231 but not the 241OR. There is zero flexibility with the 231/RC setup. You either get 4H, stock 2.71:1, or 7:1.
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I liked the low low on my rubicrawler/231 setup for the Rubicon trail. It’s unnecessary for traction like Moab.
 
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Jerry Bransford said:
For 35's and your 42RLE you need to regear to 5.38, not 5.13 which is not quite enough for 35's with the 42RLE. Gear your axles for the highway, not for your rocky trails, where 5.38 is ideal for 35's. I regeared this TJ from 4.88 to 5.38 and everything including its mpg improved significantly. Mpg went from 11 mpg to 14.6 after installing the 5.38 and the highway driving was a LOT more enjoyable too. And on the highway I consider 5.38 just adequate, I would not like the slightly lower highway rpms of 5.13 at all.

And with the Rubicon's 4:1 tcase and your automatic my strongest possible personal opinion says you don't need a Rubicrawler for your mild rock crawling like in your photo. My TJ Rubicon did lots of rock crawling on some pretty darned big rocks/extremely tough trails and it crawled beautifully with its 4:1 tcase and 42RLE automatic without a Rubicrawler. I could crawl at .01 mph if needed with that combination. :)
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Jerry,

What RPM are you seeing at 60 MPH with the 5.38s? Right now I cruise at 60 MPH and about 1850 RPM with 4.10 gears and stock tires.

I am thinking it is best to keep the RPM close to stock after I re-gear and move to 35s. By doing the math, 4.88s will give me about 1940 RPM.

But you are running 35s, and I calculate about 2140 with your set-up. Is this anywhere near what you are seeing?
 
cj cake said:
Jerry,

What RPM are you seeing at 60 MPH with the 5.38s? Right now I cruise at 60 MPH and about 1850 RPM with 4.10 gears and stock tires.

I am thinking it is best to keep the RPM close to stock after I re-gear and move to 35s. By doing the math, 4.88s will give me about 1940 RPM.

But you are running 35s, and I calculate about 2140 with your set-up. Is this anywhere near what you are seeing?
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Ok know that you do NOT want the same rpms for 35's that worked ok for smaller tires. Bigger tires require more rpms, really. And 1940 is WAY too low for 35's even at 60 mph.

For 35's and your Rubicon with the 4-speed automatic, 5.38 is barely adequate for the highway and 5.13 is the absolute minimum which I wouldn't even consider. And at 60 mph my calculator shows 2150 rpms with 35's, 5.38, and the 42RLE you and I both have. Trust me, that is BARELY adequate. I wish I could have gone to the next lower ratio from 5.38 which is 5.89 but the gears wouldn't fit onto my lockers.
 
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I am running with 31" tires and 373 gears with an automatic trans. I love the Rubicrawler it lets me run over 70 mph on the highway and is plenty low for mild trails & some rocks. It is also great on steep down hills, which I use second gear while others are using their brakes.
 
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Jerry Bransford said:
Ok know that you do NOT want the same rpms for 35's that worked ok for smaller tires. Bigger tires require more rpms, really. And 1940 is WAY too low for 35's even at 60 mph.
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The Jeep I am driving is a stock 2006 TJ Rubicon with 4.11 gears and 42RLE auto transmission, NVG 241OR transfer case, on 31" tires.

The local 4X4 shop recommended "no bigger than 4.56 gears for 35s", but you are saying 5.35s. I am just trying to figure out why.

When I brought this up, their reply was "so you are going to listen to a bunch of keyboard warriors instead of us, we've been doing this for decades."

I am listening to everyone, then I will try to figure out for myself what I will do. Your logic makes sense to me, the larger mass of the 35 will require more engine RPM to get it spinning and keep its momentum. I just have no practical experience. I have not driven any other Jeep or a 4WD on 35s before.
 
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cj cake said:
The Jeep I am driving is a stock 2006 TJ Rubicon with 4.11 gears and 42RLE auto transmission, NVG 241OR transfer case, on 31" tires.

The local 4X4 shop recommended "no bigger than 4.56 gears for 35s", but you are saying 5.35s. I am just trying to figure out why.

When I brought this up, their reply was "so you are going to listen to a bunch of keyboard warriors instead of us, we've been doing this for decades."

I am listening to everyone, then I will try to figure out for myself what I will do. Your logic makes sense to me, the larger mass of the 35 will require more engine RPM to get it spinning and keep its momentum. I just have no practical experience. I have not driven any other Jeep or a 4WD on 35s before.
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42rle has a steep overdrive that requires 5.38s for the 35” tires. Trust me, I ran 4.88s with the 42rle and 35s and it was impossible to maintain highway speed on flat ground without constantly downshifting into 3rd. 5.38s allowed me to cruise at 70 mph without issue. The 4wd shop has no clue and is not a good source of real world experience.
 
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cj cake said:
The Jeep I am driving is a stock 2006 TJ Rubicon with 4.11 gears and 42RLE auto transmission, NVG 241OR transfer case, on 31" tires.

The local 4X4 shop recommended "no bigger than 4.56 gears for 35s", but you are saying 5.35s. I am just trying to figure out why.
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The reason they're pushing 4.56 is they're clueless when it comes to how to gear for your 42RLE automatic transmission which is absolutely totally common. Your 42RLE's Overdrive ratio is .69 which drops the rpms much lower than you'd get with a manual transmission that they're used to. Different transmissions and different engine sizes and power require different axle ratios. If I had a truck with a V8 engine and manual transmission absolutely I'd gear to 4.56 for 35's but that'd be the totally wrong ratio for your 4.0 engine, 35's, and 42RLE automatic transmission. And if you had the older 3-speed automatic 4.56 would be perfect for 35's but NOT with your 4-speed 42RLE's with its stupid-steep .69 Overdrive ratio which, again, drops the rpms way too low when on the highway. If you geared to 4.56 or even 4.88 you'd be lugging the engine on the highway.

And just a personal story here.... I bought my present TJ used and the previous owner only geared it to 4.88 for 35's. He even admits now it was a stupid mistake. So I'm driving it and the engine is lugging so badly on the highway I kept having to shut the Overdrive off which then gave rpms that were a little too high. But for the most part I did my long trips with the Overdrive and it just lugged, highway driving was just miserable. And it never got better than 11 mpg on long trips. Then Revolution Gear announced their 5.38 gears and I installed them. Immediately life was good on the highway again and even my mpg jumped up to 14.6 because the engine was operating more efficiently at the slightly higher rpms.

And as I said above, 5.38 is barely enough to be good on the highway. Offroad even 4.56 would be fine with the 4:1 transfer case the Rubicon has but definitely NOT on the highway. Since you have the Rubicon which allows gearing to 5.38, don't screw up and install anything but 5.38. It's not just my recommendation, that is the one that gets recommended by everyone who knows how to gear for the 42RLE transmission you and I both have which is a different beast. And if the shop pushes back on 5.38, I'd tell them to install 5.38 as I'm requesting or I'll find a different shop that will.
 
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cj cake said:
The local 4X4 shop recommended "no bigger than 4.56 gears for 35s", but you are saying 5.35s.
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ignore their advice
cj cake said:
I am just trying to figure out why.
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hundreds of thousands of miles of combined experience
cj cake said:
When I brought this up, their reply was "so you are going to listen to a bunch of keyboard warriors instead of us, we've been doing this for decades."
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5.38s for TJs haven't been around for decades. Their info is outdated.
 
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