Best gear ratio for 1999 4.0 automatic with 31 inch tires?

Tripbus

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I recently picked up a 99 TJ Sport 4.0L auto with 31 inch tires. The Jeep seems a little lethargic especially while merging on highway. I checked the rear gear ratio and it states 3.07 on the tag.

I would like to keep this tire size and have no intention on going bigger. Based on my setup, what is the ideal gear ratio? Also, how do I confirm what gears are installed as I have no idea if it has been regeared.

If I did decide to regear, could I just buy used axles in the other common ratios - 3.73 or 4.11? What exactly would I need to change? Would I have to change both front and rear?

I am a re-gear noob so any help would be much appreciated.
 
I ran stock 3.07 gears with 31s and the 32RH for a few years after upgrading from 30s and honestly could not tell a difference. It didn’t feel quick but never has in the 21 years I’ve owned it. I did regear after moving up to 33s but did not feel like it was necessary with 31s especially for around here where’s it’s mostly flat.
 
I ran stock 3.07 gears with 31s and the 32RH for a few years after upgrading from 30s and honestly could not tell a difference. It didn’t feel quick but never has in the 21 years I’ve owned it. I did regear after moving up to 33s but did not feel like it was necessary with 31s especially for around here where’s it’s mostly flat.

This is good to know. Thanks!
 
Cheaper to swap in some 4 cylinder Jeep axles with 4.10 gears than waste money to regear for small tires. I paid $250 for both axles when I did that.

p.s. If I had little 31" tires and the 32rh auto, I'd just live with the 3.07s. Not worth the money and effort IMO.
 
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Thanks, for the responses. What should my RPM be at 65mph with 31s and 3.07 gears? Would like to confirm if my gears have been changed over the years.
 
I would want 3.73s. That would be a significant change over 3.07’s if you’re going to be on 31’s long term. On the other hand, if there is a chance of any other (larger) tire size later on then you’d want to factor that in and gear accordingly, such as 4.10 for 33’s or 4.56 for 35’s.
 
I enjoyed my 31" tyres more when I regeared to 5.13.
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I just bought an 01 3-speed Automatic 4.0 engine with 32s on a 2” lift the original owner never regeared. Not looking to increase tire size at all in future. Any recommendations on best gear ratio for the 32s? Thanks!
 
Cheaper to swap in some 4 cylinder Jeep axles with 4.10 gears than waste money to regear for small tires. I paid $250 for both axles when I did that.

p.s. If I had little 31" tires and the 32rh auto, I'd just live with the 3.07s. Not worth the money and effort IMO.

In what year did you pay $250 for the pair of 4.10 axles from a 4cyl TJ?