Gear ratio questions and advice

PalmettoStateBob

PalmettoStateBob

TJ Enthusiast
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Joined
Apr 14, 2020
Messages
130
Location
Anderson, SC
2000 TJ, 4.0, Automatic
Running 275s. Wife and I do wine vineyards in the GA, NC, and SC mountains. Mild trails but not into mudding or rocks. Not a daily driver.
I’m wanting to re gear for improved pulling on hills. I may go as high as 33s on tires someday in the far future, but no more than we drive in a year my Toyo’s will probably dry rot before I wear them out. Hell the 235’s that was on TJ when I got it finally started coming apart.
So, will I see much difference in mpg between the 4.56 and the 4.88?
Will I see much difference in pulling hills?
Is there much difference between them on take off?
 
I have the same, 4.0 auto in a 2000. For 33's you should consider 4.10s. I ran 4.10s with 33s for years and was very happy. Switched to 4.56 when I went up to 35s and am very happy there. I think 4.56 would be ok on 33s but 4.88 would be too low. YMMV
 
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Peakbagger said:
I have the same, 4.0 auto in a 2000. For 33's you should consider 4.10s. I ran 4.10s with 33s for years and was very happy. Switched to 4.56 when I went up to 35s and am very happy there. I think 4.56 would be ok on 33s but 4.88 would be too low. YMMV
Click to expand...

Was at the off road center I deal with today. He is very familiar with where we make our day trips and the mild trails we ride. He highly recommend going with the 4.10
We will probably never step up to 33’s, wife and I are both short and around 60. A 2 1/2 lift on 275’s is about her limit.
Made an appointment
 
CharlesHS said:
Never driven a 4.0L TJ with the automatic transmission.
Would 4.10s be sufficient with 32” tires for South Carolina mountain drives ?
Just curious….
Click to expand...

I'm not as knowledgeable as someone like Jerry, I also don't personally have an automatic transmission but...

From my understanding:
4.10's are the 'perfect' gearing for the 3-speed auto with 32" tires.
4.88's are the 'perfect' gearing for the 4-speed auto with 32" tires.

Gearing selection almost exclusively depends on the specific transmission in question (3-speed or 4-speed) as well as tire size.

I'm originally from SC! Know those mountains very well.
South Carolina mountains aren't worrisome enough for any concern with elevation/steepness, so I wouldn't personally bother 'going deeper' than mentioned on gears.
Whereas here in Colorado, I went as deep as possible, because elevation on these mountains and steeper road grades make SC mountains look like ant-hills. :ROFLMAO:
 
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PalmettoStateBob said:
According to every thing I have seen that is the metric for 31”
Click to expand...

That is incorrect.

Metric tires are measured in three measurements.
- First number is the width
- Second measurement is the sidewall height (measured as a percentage of the tire width)
- Last measurement is the wheel diameter.

We'll utilize '275' as you said.
I don't know any information other than what you said, but per this example we'll use a tire size of 275/70/15

275 is the tire width, measured in millimeters (approximately 10.8 inches)

70 is the 'aspect ratio'. It is the sidewall height, in relevancy to the width of the tire. This denotes that the sidewall height is 70 PERCENT of the width.
(since 275 is the width, this means each sidewall is approximately 192.5mm, or 7.6 inches)

15 is the wheel/rim size, in inches.

275/35R15 is 22.6" in diameter with a 15" wheel.
275/35R17 is 24.6" in diameter with a 17" wheel.
275/55R15 is 26.9" in diameter with a 15" wheel.
275/55R17 is 29" in diameter with a 17" wheel.

...that's enough to understand where i'm going with this.

With that being understood, a "275 tire" CAN be 35 inches in diameter, but it CAN ALSO be 23 inches in diameter.

Therefore a simple '275 is my tire size' is insufficient in determining what your actual tire size may be, and is ultimately useless in determining what gear ratio you should be using.

Long story short, saying you have a '275 tire' is not the same as stating what your tire size is.
Your tire size, in its full entirety, is needed to determine what dimensions your tires are.
 
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Here's a 29"
Screenshot_20240219_221323_Chrome.jpg


And a 27"
Screenshot_20240219_221624_Chrome.jpg
 
Less than 33" tires and a 32rh 3 spd auto i would use 3.73 gearing. That jeep will either have 3.07 or 3.73 stock. Most likely 3.73
 
zachpeakee said:
I'm not as knowledgeable as someone like Jerry, I also don't personally have an automatic transmission but...

From my understanding:
4.10's are the 'perfect' gearing for the 3-speed auto with 32" tires.
4.88's are the 'perfect' gearing for the 4-speed auto with 32" tires.

Gearing selection almost exclusively depends on the specific transmission in question (3-speed or 4-speed) as well as tire size.

I'm originally from SC! Know those mountains very well.
South Carolina mountains aren't worrisome enough for any concern with elevation/steepness, so I wouldn't personally bother 'going deeper' than mentioned on gears.
Whereas here in Colorado, I went as deep as possible, because elevation on these mountains and steeper road grades make SC mountains look like ant-hills. :ROFLMAO:
Click to expand...

Jerry Bransford said:
Yep 4.10 due to your 3-speed automatic. 4.56 and 4.88 would only be good choices for the 5-speed manual transmission for 33's and 35's.
Click to expand...

I currently have a 3.07 ratio.
That 4.10 will be a good step up
 
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