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Old 01-20-2014, 07:58 PM   #1
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Gear ratio confusion

Hello all,

I should start by saying that I'm not the most mechanically inclined and big automotive words scare me. That being said, I need some gear help.

I recently lifted my TJ and put 33x12.5 tires on it and lost boatloads of power. A fellow jeeper instructed me to regear my axles with 4.10 gears. It sounds simple enough but a lot of numbers are thrown around when I started doing research on what to buy. My stock configuration is listed below along with what I found and think to be the correct. Please let me know if I'm correct or if I'm about to blow something up.

Stock:
DJJS Dana 30/186MM Front Axle
DMEP 3.73 Rear Axle Ratio
DRKP Heavy Duty Dana 44 Rear Axle

New stuff:
G2 Axle and Gear Dana 44 4.09 Ratio
For Use With 3.91 And Up Carrier
G2 Axle and Gear Dana 30 TJ/WJ/XJ/ZJ Front Short 4.10 Ratio
For Use With 3.73 And Up Carrier

I guess my real confusion is coming from the "for use with 3.91 and up carrier" part. Do I need to buy something else or will this work?

Sorry for how Barney style this post is, I just need some help!

Thanks!

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Old 01-20-2014, 08:03 PM   #2
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What model year is your TJ, and is your transmission a manual or an automatic.

Need to know that information before any gearing advice can be given.

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Old 01-20-2014, 08:06 PM   #3
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Like I said, not the most mechanically inclined lol. But I've got a 2003 TJ sport, 5 speed manual transmission.
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Old 01-20-2014, 08:15 PM   #4
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Most popular is 4.55 4.56 for 33 tires with 5 SPd 4.0

But 4.11 4.10 works ok

My wife runs metric 33 on a rubi 5spd with 4.11
I run 33 tires and 4.56 with my 98 sport 5spd

Both are Ok
I like 4.11 better on interstate and 4.56 better off road
Both have 4.1 low transfer case
Hers stock rubi tc mine terra low tc
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Old 01-20-2014, 08:20 PM   #5
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You want 4.56 not 4.10 with the 5 speed tranny. You will also need a new carrier for the D44 so this would be a good time to install a locker or limited slip.

Make sure you source all parts for the job through the installation shop so they fully warranty their work.
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Old 01-20-2014, 08:23 PM   #6
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With your 5 speed and 33" tires, your optimum axle gear ratio should be 4:56, not 4:10.

In most axles, you have what's called a "carrier break". This means that your axle has a carrier (or locker) and it can't just use gears of any ratio. It can only use gears of a certain ratio and lower on one side of the "break", and gears of another ratio and higher on the other side of the "break." In other words, if you want to go to a numerically higher gear ratio from your current lower gear ratio, then you would have to buy a different carrier so the gears will fit properly.
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Old 01-20-2014, 08:24 PM   #7
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Quote:
Originally Posted by Fifteenwhiskey View Post
Like I said, not the most mechanically inclined lol. But I've got a 2003 TJ sport, 5 speed manual transmission.
Ok. While 4.10 would be better than what you have, it's not the optimal gear ratio for 33" tires, 5-speed manual transmission, and the 4.0L engine. What you really want is 4.56. NO, 4.56 would not be too low of a ratio and NO, 4.56 would not cause excessively high highway rpms.

15-16 years ago I made the mistake of not listening to my more expereinced friends who all recommended 4.56 for my then-33" tires and instead went with 4.10. I was not as experienced then and was scared the 4.56 would make my rpms too high. Within 2-3 days, I realized I had made a mistake going with 4.10 instead of 4.56. I was having to downshift way more than normal and that was for even gentle grades.

4.10 is the usual recommendation made by Chevy truck driving kids behind the counter, they just don't have enough experience with Jeeps to make more appropriate recommendation.

The rest of is simple... you're obviously not going to be installing the gears yourself. So do NOT buy the parts you think you need to give to the installing shop to install. Providing the gears yourself means the shop will not take care of any parts warranty issues if anything goes wrong. They'll of course say they installed them properly and the gear dealer will blame the installing shop. And it normally is the installing shop that screws up ring & pinion gear installations. It happened to me on my next regearing job when I went to 4.88. 6 weeks after a shop installed them, the gears started whining horribly 200 miles from home. Scared the crap out of me. But because I had the shop provide everything, all parts & labor, their warranty covered everything. So don't get caught in the middle of the installing shop and gear provider pointing their fingers at each other, have the shop provide everything needed.

And to make the shop's pricing on gears more competitive, push them for a significant discount from their first quote. If you can get the whole job done for $1100-1200, you did good. My last regearing job cost me $1087 but I pushed them hard for a discount. Those prices are for all parts, all labor, warranty, & everything need to regear two axles.

Good luck. And oh, did I already say not to go with 4.10 for your 33" tires?
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Old 01-20-2014, 08:37 PM   #8
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Quote:
Originally Posted by Jerry Bransford View Post
Ok. While 4.10 would be better than what you have, it's not the optimal gear ratio for 33" tires, 5-speed manual transmission, and the 4.0L engine. What you really want is 4.56. NO, 4.56 would not be too low of a ratio and NO, 4.56 would not cause excessively high highway rpms. 15-16 years ago I made the mistake of not listening to my more expereinced friends who all recommended 4.56 for my then-33" tires and instead went with 4.10. I was not as experienced then and was scared the 4.56 would make my rpms too high. Within 2-3 days, I realized I had made a mistake going with 4.10 instead of 4.56. I was having to downshift way more than normal and that was for even gentle grades. 4.10 is the usual recommendation made by Chevy truck driving kids behind the counter, they just don't have enough experience with Jeeps to make more appropriate recommendation. The rest of is simple... you're obviously not going to be installing the gears yourself. So do NOT buy the parts you think you need to give to the installing shop to install. Providing the gears yourself means the shop will not take care of any parts warranty issues if anything goes wrong. They'll of course say they installed them properly and the gear dealer will blame the installing shop. And it normally is the installing shop that screws up ring & pinion gear installations. It happened to me on my next regearing job when I went to 4.88. 6 weeks after a shop installed them, the gears started whining horribly 200 miles from home. Scared the crap out of me. But because I had the shop provide everything, all parts & labor, their warranty covered everything. So don't get caught in the middle of the installing shop and gear provider pointing their fingers at each other, have the shop provide everything needed. And to make the shop's pricing on gears more competitive, push them for a significant discount from their first quote. If you can get the whole job done for $1100-1200, you did good. My last regearing job cost me $1087 but I pushed them hard for a discount. Those prices are for all parts, all labor, warranty, & everything need to regear two axles. Good luck. And oh, did I already say not to go with 4.10 for your 33" tires?
This answered some of my upcoming questions also. Thanks Jerry
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Old 01-20-2014, 08:41 PM   #9
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I would guess Jerry, my '06 Rubi six speed with 4.10 gears would use the same advice? She's getting a small 3" lift in the spring and 33"s. glad I saw this as I thought the rubicons gearing would be fine. She's my DD, some highway, some offroading. Thanks, and with 33's what would get me back to stock gear ratio?
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Old 01-21-2014, 02:12 AM   #10
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Quote:
Originally Posted by Verf View Post
... and with 33's what would get me back to stock gear ratio?
You want a numerically higher ratio than stock to compensate for the larger and heavier tires.
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Old 01-21-2014, 10:19 AM   #11
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Quote:
Originally Posted by Verf View Post
I would guess Jerry, my '06 Rubi six speed with 4.10 gears would use the same advice? She's getting a small 3" lift in the spring and 33"s. glad I saw this as I thought the rubicons gearing would be fine. She's my DD, some highway, some offroading. Thanks, and with 33's what would get me back to stock gear ratio?
Newer Rubicons with the slightly lower ratio 6-speed transmission as opposed to the higher ratio 5-speed can get away with 4.10 gearing for 33" tires better. I would wait until you get the 33" tires to decide. See how it does with your 6-speed, it may be ok. It's more with the 5-speed where 4.10 is not a good ratio for 33" tires. Personally I'd probably go with 4.56 with the 6-speed but that's a pretty expensive job to only go from your present 4.10 to 4.56.
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Old 01-21-2014, 11:03 AM   #12
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Quote:
Originally Posted by Jerry Bransford View Post
Newer Rubicons with the slightly lower ratio 6-speed transmission as opposed to the higher ratio 5-speed can get away with 4.10 gearing for 33" tires better. I would wait until you get the 33" tires to decide. See how it does with your 6-speed, it may be ok. It's more with the 5-speed where 4.10 is not a good ratio for 33" tires. Personally I'd probably go with 4.56 with the 6-speed but that's a pretty expensive job to only go from your present 4.10 to 4.56.
x2

I have been driving 33s with 3.73 for a year now. Although not ideal, I would stick with 4.10s if it doesn't bother you until you decide for a larger tire (it happens). I plan on skipping 4.56 and doing 4.88 with 35s
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Old 01-21-2014, 11:54 AM   #13
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Gear Ratio Calculator
This gear calculator helped me when I was trying to decide what gears to go to.
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Old 01-21-2014, 10:01 PM   #14
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Thanks all!

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