Best DD gear ratio for 31s or 33s: 4.0 liter, NV3550 - JeepForum.com
 
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post #1 of 11 Old 07-29-2010, 11:14 PM Thread Starter
Maverickxeo
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Best DD gear ratio for 31s or 33s: 4.0 liter, NV3550

I have an 02 TJ 4.0L 5 speed Sport. I have a 4" suspension lift, running 31" tires, and stock gear ratios (3.73). I was just wondering if I need to regear for the tires? If it matters at all, when these tires are gone, I would like some 33" tires in the same width (10.50).

Currently, I get about 18MPG US highway. This is a commuting vehicle (crazy, I know) so I would like to keep my MPG above 16 at least.

So, what gears would be best for highway driving, running 31" to 33" tires, while still maintaining decent mileage?

(Also, how 'hard' is it to change gears, or how many hours labour is it?)

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post #2 of 11 Old 07-29-2010, 11:21 PM
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I wouldn't re-gear for 31" tires. It won't make much of a difference to justify the cost. 3.73 gears work fine for 31s anyway. For 33s and your NV3550 tranny, 4.56 is a superb ratio. You shouldn't have to worry about mpg on the freeway with that combo especially if you run a narrow 10.50" wide tire.

As far as gearing costs, it will vary depending where you live. Around here average labor costs for a re-gear is $200-$300 an axle not including parts of course. If you re-gear it would also be a good time to install lockers if you have plan them so you won't have to pay for the labor a second time in the future.

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post #3 of 11 Old 07-29-2010, 11:22 PM
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From a cost prospective of what I've seen regearing go for, you are much better sucking up the worse mileage and ride with the 3.73s. But as for any kind of power loss, I can offer you no insight other than post 5 in this thread: https://www.jeepforum.com/forum/f9/32...regear-107592/

Heres an idea of the prices you are looking at to regear: https://www.jeepforum.com/forum/f9/co...earing-523939/
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post #4 of 11 Old 07-29-2010, 11:32 PM Thread Starter
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I forgot to mention the amount of highway I actually do... its about 100KM per trip; 4-5 days a week. Would it be the best to keep the 3.73s still until I put on 33" tires?
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post #5 of 11 Old 07-30-2010, 12:53 AM
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Quote:
Originally Posted by Maverickxeo View Post
I forgot to mention the amount of highway I actually do... its about 100KM per trip; 4-5 days a week. Would it be the best to keep the 3.73s still until I put on 33" tires?
No I once ran that combo for quite a while. It was no fun at all. You'll lose the ability to use 5th gear and pretty much have to keep it in 4th. In 4th gear with 33s you'll be taching close to 3k rpms at 65mph. Trying to run in 5th on the freeway will kill your mileage since your engine will be lugging as it won't be in the power band. Running in 4th will also decrease your fuel economy as the rpms will be too high. 3.73s and 33" tires are less than ideal. 4.56 gears will put your rpms where they need to be for 33" tires.

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post #6 of 11 Old 07-30-2010, 03:17 AM Thread Starter
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Originally Posted by BYuen View Post
No I once ran that combo for quite a while. It was no fun at all. You'll lose the ability to use 5th gear and pretty much have to keep it in 4th. In 4th gear with 33s you'll be taching close to 3k rpms at 65mph. Trying to run in 5th on the freeway will kill your mileage since your engine will be lugging as it won't be in the power band. Running in 4th will also decrease your fuel economy as the rpms will be too high. 3.73s and 33" tires are less than ideal. 4.56 gears will put your rpms where they need to be for 33" tires.
Okay then, Ill try to save a bit extra for when I go for 33s. You have 4.56s and 33" tires, I assume? How is it on gas anyways?
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post #7 of 11 Old 07-30-2010, 04:37 AM
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I averaged 20 mpg highway with 35's and 3.73 gears,so the gas mileage shouldn't get worse.
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post #8 of 11 Old 07-30-2010, 06:37 AM
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Originally Posted by Maverickxeo View Post
Okay then, Ill try to save a bit extra for when I go for 33s. You have 4.56s and 33" tires, I assume? How is it on gas anyways?
I had 3.73s and 33s. Then I regeared to 4.88s and ran them with 33s for a little over a year until I could get 35s. 4.88s and 33s were definitely on the low side (ideal ratio for 35s), but imo it was still better than not having enough gear with 3.73s. Currently with 35x12.50s I get around 17 mpg freeway and 14-15 city. That's with a pretty heavy TJ and beastly 35" MTR Kevlars which are 67 lbs each.

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post #9 of 11 Old 07-30-2010, 06:39 AM
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I have 33's / a 3.73 and it runs fine. I drive 35 miles to work, all interstate, and use 5th gear with no problems. I average about 18-19 mpg and 70 mpg is good for 2100 rpm. I would not regear. If you choose to, don't go lower than 4.10. Just my 2 cents.
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post #10 of 11 Old 07-30-2010, 06:40 AM
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Originally Posted by TheBoogieman View Post
I averaged 20 mpg highway with 35's and 3.73 gears,so the gas mileage shouldn't get worse.
I don't know how you did it. C'ville is not that flat!

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post #11 of 11 Old 07-30-2010, 06:54 AM
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Originally Posted by wkrowe65 View Post
I have 33's / a 3.73 and it runs fine. I drive 35 miles to work, all interstate, and use 5th gear with no problems. I average about 18-19 mpg and 70 mpg is good for 2100 rpm. I would not regear. If you choose to, don't go lower than 4.10. Just my 2 cents.
Just want to make sure we're comparing apples to apples here. What tranny are you running? If you're running the 3 spd auto without an overdrive, then I would say 3.73s would be adequate with 33s. If you have the AX15, have you ever driven another TJ with lower gears and 33s? I guarantee you'll like it much better. With 3.73 gears, 33s, and the NV3550 I always had trouble maintaining speed on the highway. I would have to downshift on any type of grade. I guess if I lived where everything was flat, I would have been satisfied with 3.73s and 33s.

There are plenty of threads on JF about gearing and most all will agree that 4.56s is the ideal ratio for 33s if you have either 5speed trannies. Many who might say otherwise just haven't experienced for themselves what it's like to have the proper gear ratio for the right tire size. And when they do, they realize what they have been missing out on

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3.73 , 31s , 33s , 4.0 , 4.56 , 5 speed , gearing , nv3550 , tj , wrangler

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