Stock Rubicon gearing vs 33s with 4.56

Rut Row

Rut Row

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Out of curiosity, I loaded the stock Rubicon data and my regeared data into the calculator at the Grimm Jeeper's gear ratio calculator. http://www.grimmjeeper.com/gears.html

Check the attached. My '03 Rubi with 33s and 4.56 gears is almost exactly the same as the stock Rubi. BTW, I have a NV3550 transmission.

Next trip out I'm going to check that against actual RPMs, MPH, etc.

IMHO, this confirms @Jerry Bransford assertion that 4.56 is the right ratio for 33" tire size and a 5-speed. Unless of course, you are into serious rock crawling. Alas, I'm a mere mortal and quite happy with moderate wheeling.
 

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There are many different stock combinations that land at different cruising rpm. I don’t think any specific one factory setup is correct. Personally on 33’s with a 5 speed I’d rather have 4.88 and save the 4.56 for 30-31’s.

Jerry’s advice comes from many years ago where commonly people chose 4.10 for 33’s (no clue why that started but it did) and Jerry and a few others didn’t like that so they went one notch deeper and recommended others do the same. These days, many folks have gone even further and like that even better.
 
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Rut Row said:
Out of curiosity, I loaded the stock Rubicon data and my regeared data into the calculator at the Grimm Jeeper's gear ratio calculator. http://www.grimmjeeper.com/gears.html

Check the attached. My '03 Rubi with 33s and 4.56 gears is almost exactly the same as the stock Rubi. BTW, I have a NV3550 transmission.

Next trip out I'm going to check that against actual RPMs, MPH, etc.

IMHO, this confirms @Jerry Bransford assertion that 4.56 is the right ratio for 33" tire size and a 5-speed. Unless of course, you are into serious rock crawling. Alas, I'm a mere mortal and quite happy with moderate wheeling.
Click to expand...

Jerry is wrong about a lot of his gearing recommendations.
 
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machoheadgames said:
There are many different stock combinations that land at different cruising rpm. I don’t think any specific one factory setup is correct. Personally on 33’s with a 5 speed I’d rather have 4.88 and save the 4.56 for 30-31’s.

Jerry’s advice comes from many years ago where commonly people chose 4.10 for 33’s (no clue why that started but it did) and Jerry and a few others didn’t like that so they went one notch deeper and recommended others do the same. These days, many folks have gone even further and like that even better.
Click to expand...

No, there is only one stock combination for the 2003 Rubi. What I used is how it came from the factory according to the build sheet. The Rubi came with 4.11 gears.
 
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Rut Row said:
What I used is the stock configuration for the Rubi as it came from the factory according to the build sheet. The Rubi came with 4.11 gears.
Click to expand...

I understand that - what I’m saying is that there were many stock configurations that all land at different rpm. In other words, there is nothing to really say the rubi setup is “correct” and what should be followed.
 
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PNW_LJ said:
Yes.
Click to expand...

Here is a list of TJ factory gearing from lowest to highest RPMs. The only difference being the transmission.

42rle / 29.5" /3.73 = 2052rpm @ 70mph
NV3550/29.5"/3.73 = 2320rpm @ 70mph
AX-15 / 29.5" /3.73 = 2349rpm @ 70mph
NSG370/29.5"/3.73 = 2498rpm @ 70mph
32rh / 29.5" / 3.73 = 2974rpm @ 70mph
 
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machoheadgames said:
I understand that - what I’m saying is that there were many stock configurations that all land at different rpm. In other words, there is nothing to really say the rubi setup is “correct” and what should be followed.
Click to expand...

understood.
jjvw said:
The Rubicon came off the assembly line with the same gearing for both the NV3550 and the 42rle. Were they both correct
jjvw said:
The Rubicon came off the assembly line with the same gearing for both the NV3550 and the 42rle. Were they both correct?
Click to expand...
Click to expand...
that all depends on how you define correct, eh?
 
jjvw said:
Here is a list of TJ factory gearing from lowest to highest RPMs. The only difference being the transmission.

42rle / 29.5" /3.73 = 2052rpm @ 70mph
NV3550/29.5"/3.73 = 2320rpm @ 70mph
AX-15 / 29.5" /3.73 = 2349rpm @ 70mph
NSG370/29.5"/3.73 = 2498rpm @ 70mph
32rh / 29.5" / 3.73 = 2974rpm @ 70mph
Click to expand...

I was kidding. These gearing discussions often remind me of the “my truth” discussions we had in my philosophy class discussions.


I’m curious, how do you define what correct gearing is?
 
PNW_LJ said:
...


I’m curious, how do you define what correct gearing is?
Click to expand...

Several things, starting with the factory gearing of the 32rh being as deep as it is right off the assembly line. This is deeper gearing than the 3000rpm at 75mph that I have been advocating from my personal experience for many many years.
 
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jjvw said:
Several things, starting with the factory gearing of the 32rh being as deep as it is right off the assembly line. This is deeper gearing than the 3000rpm at 75mph that I have been advocating from my personal experience for many many years.
Click to expand...

How do we know whether Jeep got it right with the 32RH?
 
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PNW_LJ said:
How do we know whether Jeep got it right with the 32RH?
Click to expand...

I'll let you agonize over that. All I know and care about is that after 150k miles, several tire sizes and both the nv3550 and now the 42rle pushing 35s, my experience has been that higher rpms have always been preferable over lower rpms for both on and off-road.
 
jjvw said:
I'll let you agonize over that. All I know and care about is that after 150k miles, several tire sizes and both the nv3550 and now the 42rle pushing 35s, my experience has been that higher rpms have always been preferable over lower rpms for both on and off-road.
Click to expand...

That’s my point. Your recommendation is based on your personal experience. Not some categorical understanding of the ideal gear ratio.

My own desire to regear as deeply as possible, is based on previously owning a similarly undergeared SUV (0.62:1 overdrive I believe).

These gearing discussions are nothing more than “my truths”, some being more commonly accepted than others.
 
jjvw said:
Here is a list of TJ factory gearing from lowest to highest RPMs. The only difference being the transmission.

42rle / 29.5" /3.73 = 2052rpm @ 70mph
NV3550/29.5"/3.73 = 2320rpm @ 70mph
AX-15 / 29.5" /3.73 = 2349rpm @ 70mph
NSG370/29.5"/3.73 = 2498rpm @ 70mph
32rh / 29.5" / 3.73 = 2974rpm @ 70mph
Click to expand...

Ah, but we got 3.07 for export models in the UK.
 
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Anyone who thinks Chrysler did it *this* way, so it must be right, doesn't understand Chrysler's design criteria. While trying to build a good on-road/off-road vehicle, they were also aiming for specific manufacturing costs, gas mileage, government requirements. And they were selling to trail runners, beach drivers, rock crawlers, but 95% to street drivers.

They delivered the ideal gearing — ideal for Chrysler, not for each of us with our own criteria.
 
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PNW_LJ said:
That’s my point. Your recommendation is based on your personal experience. Not some categorical understanding of the ideal gear ratio.

...
Click to expand...

Correct. My personal experiences come from not wanting a sluggish Jeep and being pleased with not having it be more sluggish than it is.
 
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