Do i need to Regear my JL RUBICON with 35 inch tires?

Toycrusher

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I run 37s with a manual and 4.10 is just fine.

Don't get hung up on wanting to reach 6th gear or 8th gear (if auto). Just run where the motor is happy and you'll be fine.





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HeavyUser

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I run 37s with a manual and 4.10 is just fine.

Don't get hung up on wanting to reach 6th gear or 8th gear (if auto). Just run where the motor is happy and you'll be fine.
You having to ride the clutch at all when going up rocky inclines when offroading?
 

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You having to ride the clutch at all when going up rocky inclines when offroading?
I did Christmas mountain in West Texas in 2wd high with rear locked. It's a pretty steady climb at about 20 degrees with several switchbacks and a few technical sections. Only had to slip clutch in a couple spots as I was able to maintain about 4mph for most of it. In low I could have done it in 3rd with no problem.

With the centerforce clutch I have now, I'm positive I could crawl it 2wd high at about 2mph without stalling and without slipping the clutch.
 

HeavyUser

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I did Christmas mountain in West Texas in 2wd high with rear locked. It's a pretty steady climb at about 20 degrees with several switchbacks and a few technical sections. Only had to slip clutch in a couple spots as I was able to maintain about 4mph for most of it. In low I could have done it in 3rd with no problem.

With the centerforce clutch I have now, I'm positive I could crawl it 2wd high at about 2mph without stalling and without slipping the clutch.
Damn, I have issue stalling in 4h going up 19* inclines unless I ride the clutch... this is on stock 33s..... lol
 

Toycrusher

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Damn, I have issue stalling in 4h going up 19* inclines unless I ride the clutch... this is on stock 33s..... lol
Hmmm. that seems strange. Definitely running a Rubicon right? ;):like:

More seriously, I did keep my foot in the gas and at about 4mph I was going near WOT to keep climbing which was definitely lugging the motor bad. Why did I do it? Stupidly it's cause my buddy was in his 4Runner in 4 low and I wanted to brag that I didn't have to touch 4wd to make the climb. I did the run back down the hill in 4-lo for compression braking rather than riding brakes.
 

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I run 37s with a manual and 4.10 is just fine.

Don't get hung up on wanting to reach 6th gear or 8th gear (if auto). Just run where the motor is happy and you'll be fine.
I get so disturbed when I'm on the highway and my Jeep Auto is in 6th or 7th instead of 8th! I blame the 35" tires and second guess installing them. Last week I had the stock 33's on for about a 10 mile drive and the tranny was still preferring 6th or 7th in simalar situations. I have come to the conclusion that I may be a little insane and that I need to turn off the indicator that tells me which gear the tranny is using! I can't have the battery percentage shown on my cell phone either. :headbang:
 

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I get so disturbed when I'm on the highway and my Jeep Auto is in 6th or 7th instead of 8th! I blame the 35" tires and second guess installing them. Last week I had the stock 33's on for about a 10 mile drive and the tranny was still preferring 6th or 7th in simalar situations. I have come to the conclusion that I may be a little insane and that I need to turn off the indicator that tells me which gear the tranny is using! I can't have the battery percentage shown on my cell phone either. :headbang:
haha. I can relate. Once I "know" something, i can't not think about it. But you should probably turn the indicator off. ;) The gear its in is all relative. Its just a different RPM and the engine is just trying to keep balance power and economy. My first jeeps were 5 speeds and did just fine.
 

HeavyUser

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Hmmm. that seems strange. Definitely running a Rubicon right? ;):like:

More seriously, I did keep my foot in the gas and at about 4mph I was going near WOT to keep climbing which was definitely lugging the motor bad. Why did I do it? Stupidly it's cause my buddy was in his 4Runner in 4 low and I wanted to brag that I didn't have to touch 4wd to make the climb. I did the run back down the hill in 4-lo for compression braking rather than riding brakes.
Lol, of course :P

I guess that makes sense that you were WOT. I was more feathering the skinny pedal.....

Anyway, I'm def interested to see how it rides on 37s this weekend. Only mod I did was fender chop front and rear.
 

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I get so disturbed when I'm on the highway and my Jeep Auto is in 6th or 7th instead of 8th! I blame the 35" tires and second guess installing them. Last week I had the stock 33's on for about a 10 mile drive and the tranny was still preferring 6th or 7th in simalar situations. I have come to the conclusion that I may be a little insane and that I need to turn off the indicator that tells me which gear the tranny is using! I can't have the battery percentage shown on my cell phone either. :headbang:
:CWL: Yeah. I've done lots of experimenting and it doesn't seem to matter if I'm running 4th or 6th, fuel economy doesn't improve :CWL:
 

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I get so disturbed when I'm on the highway and my Jeep Auto is in 6th or 7th instead of 8th! I blame the 35" tires and second guess installing them. Last week I had the stock 33's on for about a 10 mile drive and the tranny was still preferring 6th or 7th in simalar situations. I have come to the conclusion that I may be a little insane and that I need to turn off the indicator that tells me which gear the tranny is using! I can't have the battery percentage shown on my cell phone either. :headbang:
If you don't reprogram for the change in tire size, the auto trans won't shift or perform like it should. I just recently switched from 315/70-17 ko2's to a set of 38x13.5 Milestar Pat's. I told the shop to not hook any programmers up to the jeep because I have a Tazer Mini installed and can adjust for the larger tire size myself. I drove it about 10 miles before making the change and the shift points were way off and it wouldn't upshift to 7th. After adjusting, it was right as rain again. Cruising at 70-75, it goes into 8th just fine but it takes less than before to make it downshift to 7th to pull any type of grade.
 

psdtime

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If you don't reprogram for the change in tire size, the auto trans won't shift or perform like it should. I just recently switched from 315/70-17 ko2's to a set of 38x13.5 Milestar Pat's. I told the shop to not hook any programmers up to the jeep because I have a Tazer Mini installed and can adjust for the larger tire size myself. I drove it about 10 miles before making the change and the shift points were way off and it wouldn't upshift to 7th. After adjusting, it was right as rain again. Cruising at 70-75, it goes into 8th just fine but it takes less than before to make it downshift to 7th to pull any type of grade.
Yes, before I knew that the Tazer existed, I bought a Superchips Flashcal to correct the tire size. Although I like the integration with the Tazer, is there any other reason to switch? The Flashcal allows me to change the tire size and also things like fog light dropout, TPMS, turning of the engine stop thing. Seems like most of the functions of the Tazer are present in the Flashcal.
 

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If you don't reprogram for the change in tire size, the auto trans won't shift or perform like it should. I just recently switched from 315/70-17 ko2's to a set of 38x13.5 Milestar Pat's. I told the shop to not hook any programmers up to the jeep because I have a Tazer Mini installed and can adjust for the larger tire size myself. I drove it about 10 miles before making the change and the shift points were way off and it wouldn't upshift to 7th. After adjusting, it was right as rain again. Cruising at 70-75, it goes into 8th just fine but it takes less than before to make it downshift to 7th to pull any type of grade.
Are you regeared? I wouldn't expect 38s to hit 8th gear unless it's downhill with a tailwind.
 

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I'm running 35s on my Sahara (3.45 gears), and it's fine. Would 4.56 or 4.88 be better? Probably. But I off-road with the Sahara too, and it seems to handle everything I like to do just fine. I suspect that if I was into heavy duty rock crawling, I'd want to upgrade. But then I'd probably go to a Rubicon anyway.
 

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35 x 12.5" on 3.45 sport here. It is 3.45 and is way to low. 4.10 would be minimum i think should be ran. I would like to go to 4.88 or 5.13 for 37s. The gearing mostly bothers me for highway/freeway/incline driving and on windy days. As for wheeling, higher gears would be nicer so I can minimize clutch and gas with braking during tricky situations. But i guess thats part of the fun of a manual.
 

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To the OP, Id also toss your wheel weight into the equation. I’m sure some guys are running heavier 35 set ups than some who are running 37’s on stock aluminum Rubi wheels (21 lbs). I run 35 E rated KO2’s on the stock Rubi wheels w/ zero issue. Tazer Lite for reprogramming gears, tps sensor and speedo.
 

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