Anyone run 4.88s with 32" tires? - JKowners.com : Jeep Wrangler JK Forum
 
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post #1 of 14 Old 01-20-2010, 10:12 PM Thread Starter
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Question Anyone run 4.88s with 32" tires?

I have a 2010 Rubicon (auto), and as most of you know its SLOW.

In all the regear threads I searched, no one mentions regearing with stock tires for better performance.

I may go to bigger tires as the Jeep ages, but thats not a concern now.

Has anyone regeared and kept the stock tires?

Anyone put stockers on just to see after gears?

This is a daily driver, about 80 miles a day, so MPG is as much a concern as it can be with the flying brick. I'd like to stay out of the single digits.

I have 4.10s now, so maybe 4.56 or 4.88?

I had an '94 ZJ that blew a diff, so I regeared it to 4.56 during the repair. With a V-8 and 31s it was not slow.

This isn't a cost/benefit excercise. I'm looking for your impression of the performance and any data on MPG. The Jeep only gets heavier from here, and slower....

Last edited by Wubicon; 01-20-2010 at 10:25 PM.
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post #2 of 14 Old 01-20-2010, 10:18 PM
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4.10s u should be getting 18-20mpg... thats what i was getting.. i have 5.13s and 37's and im getiin 15mpg...

dont waste ur money yet and regear.. it pointless and stupid..

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post #3 of 14 Old 01-20-2010, 10:24 PM Thread Starter
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I am getting about 18MPG now, so that confirms that.

Have you corrected your speedo so the MPG you mention is real?

Have you ever tried smaller tires with the 5.13s?

Lower gears will improve the performance, I'm just trying to decide how low to go, and how large the side effects might be.
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post #4 of 14 Old 01-20-2010, 10:34 PM
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yea i corrected my speedo with procal.. and i ran 35's with my 5.13s for awhile.. u actually lose ur high end speed cause it makes ur rpms higher.. so i would say i maybe got 16-17mpg with 35's

07 2dr Rubicon - Teraflex 6" LA - 37 KM2's - LoD rear bumper - Rockhard front stubby - Poison Spyder Flares - etc.

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post #5 of 14 Old 01-20-2010, 10:43 PM Thread Starter
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My math shows 35s with 5.13s to be like 32s with 4.56s (or pretty close).

When you say you lost high end speed, what are you limited to?

I don't get to go much over 70 here anyway....
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post #6 of 14 Old 01-21-2010, 07:58 AM
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I had 4.88 gears installed on a six speed manual and ran the factory 225/16's for a couple hundred miles....it was super low. But my guess is it wouldn't be terrible with 32's or 33's especially with an automatic. Don't know if this helps

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post #7 of 14 Old 01-21-2010, 08:08 AM
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Having a deeper gear installed will enhance performance but will not improve gas mileage, it will make it worse. You will be turning a higher RPM at all speeds compared to that of the stock 4.10's. Hell I have 3.73 gears and my mileage sucks.

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post #8 of 14 Old 01-21-2010, 08:36 AM Thread Starter
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I know MPG will go down, I'm just looking for data on maybe how much?
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post #9 of 14 Old 01-21-2010, 04:13 PM
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5.13's and 32's I'm getting 15mpg. I push 3K at 65 MPH.

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post #10 of 14 Old 01-21-2010, 04:28 PM Thread Starter
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How is the performance with the 5.13s?

Most people don't put a stopwatch on Jeeps, but how does it feel "seat of the pants"?
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post #11 of 14 Old 01-21-2010, 04:58 PM
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Quote:
Originally Posted by Wubicon View Post
How is the performance with the 5.13s?

Most people don't put a stopwatch on Jeeps, but how does it feel "seat of the pants"?
The same but you top out faster. It's a bit wierd, It almost becomes a 5 speed. You can start out in 2nd and 6th is the old 5th. I'm mounting the last of my 37's tomorrow so if you want something a bit more specific ask and I'll check it out. I will say 4L in 1st is low, you can wind the motor out and the speedo comes just off the peg. LOL

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This is exactly why we need to practice proper gun control.

If he was aiming down the sights correctly and had plenty of practice rounds under his belt, there would only be one side of this story.
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post #12 of 14 Old 01-21-2010, 05:37 PM
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We installed 5.13's in an automatic Rubicon JK with factory tires. The owner (and older gentleman who drives slower than I do) loves it, but it did lose him 1-2 MPG overall.


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post #13 of 14 Old 01-21-2010, 08:37 PM Thread Starter
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Quote:
Originally Posted by TeraFlex View Post
We installed 5.13's in an automatic Rubicon JK with factory tires. The owner (and older gentleman who drives slower than I do) loves it, but it did lose him 1-2 MPG overall.
Sounds good. So I could guess I'd lose 1-2 MPG (or less) with 4.88s.

Thanks.

Anyone else?
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post #14 of 14 Old 01-22-2010, 10:22 PM
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I have 4.88's and ran the stock Rubicon tires for about 6 months until I found a deal on some 35's to run on the street. My mileage with the stock Rubicon tires was about 17, and with the 35" MTZ's it is around 16. (+/- 1 depending on weather and external factors). The power was much better with 4.88's, but in the end it is still an underpowered motor on a vehicle with the aerodynamics of a shoe box.
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