4:1 Rubicon transfer case swap?

DylanM345 said:
. . . I wouldn't mind a 4:1 ratio compared to the current 2.7:1
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Be careful what you wish for. I have a Rubicon with the NV241OR 4:1 transfer case. On many trails I found the low range ratio to be too low (i.e. engine rpm higher than my liking) and wished I had a 2.5-2.7:1 low range ratio for those situations.

Since I have a 42RLE automatic transmission I resolved the issue with a Rubi-Crawler so I now have 2.72:1, 4.0:1 and 10.88:1 low range ratios. Of those ratios I use 2.72:1 the most - by a wide margin. On a run Father's Day Weekend I didn't really need the 4.0:1 low range at all.

A rudimentary cost/benefit analysis suggests that unless you are into technical rock crawling you might be better off changing your 3.73 axle gear ratio to better suit your 33" tires and leaving your transfer case alone.

Food for thought.
 
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Mr. Bills said:
Be careful what you wish for. I have a Rubicon with the NV241OR 4:1 transfer case. On many trails I found the low range ratio to be too low (i.e. engine rpm higher than my liking) and wished I had a 2.5-2.7:1 low range ratio for those situations.

Since I have a 42RLE automatic transmission I resolved the issue with a Rubi-Crawler so I now have 2.72:1, 4.0:1 and 10.88:1 low range ratios. Of those ratios I use 2.72:1 the most - by a wide margin. On a run Father's Day Weekend I didn't really need the 4.0:1 low range at all.

A rudimentary cost/benefit analysis suggests that unless you are into technical rock crawling you might be better off changing your 3.73 axle gear ratio to better suit your 33" tires and leaving your transfer case alone.

Food for thought.
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I whole heartedly agree here. I wish I had the option for a rubicrawler. I have the unique opportunity to do rock crawling, mud bogging, sand dunes and forest roads, all within about a 2 hour drive. I've seriously contemplated selling the 241 T-case for a standard 231 or going flipped dana 300 with a twin stick.
 
DylanM345 said:
the teralow kits apparently had a bad problem of grenading when you got into the higher rpms, they just straight up started breaking.
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Interesting to know why...
I had a TeraLow 4:1 in the '98 XJ 4.0L AX-15 with 33s and 4.56s for almost 20 years and never had a problem....
I used the synthetic Redline ATF +4 and changed it every 2 years.
Spent a lot of years in the Moab, Anza Borrego Desert and Big Bear Mountain; the trails varied between dirt, rock crawling, desert and some river crossings.
Either I was lucky or the use of the synthetic ATF was why the 4:1 lasted so long.
 
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CharlesHS said:
Interesting to know why...
I had a TeraLow 4:1 in the '98 XJ 4.0L AX-15 with 33s and 4.56s for almost 20 years and never had a problem....
I used the synthetic Redline ATF +4 and changed it every 2 years.
Spent a lot of years in the Moab, Anza Borrego Desert and Big Bear Mountain; the trails varied between dirt, rock crawling, desert and some river crossings.
Either I was lucky or the use of the synthetic ATF was why the 4:1 lasted so long.
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Did you keep your rpms down? Aren’t they limited to 2500?
 
CharlesHS said:
Interesting to know why...
I had a TeraLow 4:1 in the '98 XJ 4.0L AX-15 with 33s and 4.56s for almost 20 years and never had a problem....
I used the synthetic Redline ATF +4 and changed it every 2 years.
The type of trails that I ran varied;
Spent a lot of years in the Moab, Anza Borrego Desert and Big Bear Mountain; the trails varied between dirt, rock crawling, desert and some river crossings.
Either I was lucky or the use of the synthetic ATF was why the 4:1 lasted so long.
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The issue was the planet gears and the sun gear were too small. What happens is if you run in the lower trans gear at high RPM, you overspeed the planet gears and they blow up or smoke the axles they ride on.

If you ever compare to two gear sets side x side, you can see why the 241 is a superior gear set.
 
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Definitely the 241OR is a better transfer case (stronger planetary gears and wider chain), but I had the TeraLow many years before the 241OR was available or I would have installed the 241OR instead.
Yes.... the NP231 transfer case planetary gears would buzz past certain RPMs which signalled to shift to the next higher gear in the AX-15.
 
mrblaine said:
You didn't by any chance happen to be out there with a very confused individual in a green 02 also on 33's?
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Yes I was😂, I just did not want to get involved because he is a close friend of mine and I try to remain friends with everyone on this forum :)
 
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DylanM345 said:
Yes I was😂, I just did not want to get involved because he is a close friend of mine and I try to remain friends with everyone on this forum :)
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So, what trail did YOU run? And yes, remaining friends with the locals in the event you wind up on the same trail together is always better than not.
 
mrblaine said:
So, what trail did YOU run? And yes, remaining friends with the locals in the event you wind up on the same trail together is always better than not.
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My jeep was actually acting up the first day we went to check out chocolate thunder so I hopped in my buddys can am for the day. Later I took my jeep in a cool spot of either the front or back of backdoor(cant remember). Nothing crazy, but we couldnt continue because there was a literal wall of a rock that was taller than our jeeps. I am not very experienced, so I didnt do anything crazy considering I am on stock arms, stock tcase height(with a few washers to help with vibes) 1.25"BL and 1"MML. I learned quite a bit and nothing on my rig was broken. I touched my stock gas tank skid, transfer case skid, and slightly scraped the bottom of my dana 30. It was very fun. and I got to put to use my 14 day old 33/12.5/15 KM3s
 
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DylanM345 said:
My jeep was actually acting up the first day we went to check out chocolate thunder so I hopped in my buddys can am for the day. Later I took my jeep in a cool spot of either the front or back of backdoor(cant remember). Nothing crazy, but we couldnt continue because there was a literal wall of a rock that was taller than our jeeps. I am not very experienced, so I didnt do anything crazy considering I am on stock arms, stock tcase height(with a few washers to help with vibes) 1.25"BL and 1"MML. I learned quite a bit and nothing on my rig was broken. I touched my stock gas tank skid, transfer case skid, and slightly scraped the bottom of my dana 30. It was very fun.
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When ya'll rigs grow up a bit, you really need to hit a few trails out there. It is an eye opening experience that is beyond entertaining.
 
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mrblaine said:
When ya'll rigs grow up a bit, you really need to hit a few trails out there. It is an eye opening experience that is beyond entertaining.
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I plan to. I saw a bunch of cool trophy trucks and rock buggys which I would plan on building as I get older. Being out there now as a 17 year old really surprised me how much cool stuff there was. Now i just need to figure out what LazerTown is :LOL: The sign on the front makes it seem like they dont like visitors... LOL
 
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DylanM345 said:
I plan to. I saw a bunch of cool trophy trucks and rock buggys which I would plan on building as I get older. Being out there now as a 17 year old really surprised me how much cool stuff there was. Now i just need to figure out what LazerTown is :LOL: The sign on the front makes it seem like they dont like visitors... LOL
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Laser Town is private property owned by my good friend Cody Waggoner and his Dad. They own a laser cutting and fabrication company called Laser Nut over in Norco. He runs Ultra 4 in a very high performance Ultra 4 rig.
 
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mrblaine said:
Laser Town is private property owned by my good friend Cody Waggoner and his Dad. They own a laser cutting and fabrication company called Laser Nut over in Norco. He runs Ultra 4 in a very high performance Ultra 4 rig.
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I had a feeling it was some ultra4 guys, pretty cool place though!
 
aidanm said:
Is the np241 a direct bolt on over the 231?
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Yes and no. The 241 only has one input shaft length so that may have to be dealt with on some transmissions. Other than that and that really isn't a big issue, it is a direct bolt in. The transmission mounting methods vary somewhat so some custom work will need to be done there. Most folks are not using these in a 100% stock belly skid application so it is already custom.

It does bolt up directly to any trans the TJ 231J was bolted to though.
 
mrblaine said:
Yes and no. The 241 only has one input shaft length so that may have to be dealt with on some transmissions.
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Any opinions as to how much of the output shaft of the tranny needs to interface (overlap?) with the input shaft of the transfer case? I'm doing this with an AX15 which I know has been done before, but just eyeballing the two, it doesn't look like a ton of engagement.
 
SkylinesSuck said:
Any opinions as to how much of the output shaft of the tranny needs to interface (overlap?) with the input shaft of the transfer case? I'm doing this with an AX15 which I know has been done before, but just eyeballing the two, it doesn't look like a ton of engagement.
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I don't know that I'd be happy with less than around an inch or so, maybe 3/4" but that's probably pushing it.
 
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