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Old 08-25-2009, 03:52 PM   #1
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Gear ratios??

I have been confused for awhile now about gear ratios... anybody out there have a crash course on what the numbers mean? My 04 has a Dana 44 rear axle and curious what stock gears came in it?
What gear ratios are common for hard core wheelers and what gear ratio is most common in stock jeeps?
I want to have a better understanding of what the numbers represent so I can relate to the other Jeep junkies out there!

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Old 08-25-2009, 04:28 PM   #2
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Well im not really much of a gear person but I can tell you that on the cover of your d44 there should be a little metal tag. Take a wire brush, clean it off and there should be numbers on there representing your gear ratio.

If not then you can jack up the back of the jeep so the tires are off the ground. Slowly spin a rear tire 1 revolution, and count how many revolutions the u-joint or yoke makes. I think each revolution represents 100. So in other words if it spins 3 1/2 times that would mean you have 3.55 gears. If it makes 3 turns and then almost another full turn it could be 3.73 gears, and so on.

As far as what gears to run, that all depends on your tire size. Someone else could explain better than me.

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Old 08-25-2009, 05:36 PM   #3
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in a nut shell... rotational mass.

exp... 30'' tire and 3.73 gears = typical stock combo. Takes 3.73 rotations of the pinion gear to rotate the tire 1 full rotation.

35'' tire and 3.73 gears = do to the larger diameter of the tire it will require more than 3.73 rotations of the pinion gear to rotate the tire 1 full rotation.

Does that help some with the understanding and reason why you need lower gears for larger tires?

Also as KBR97 suggested there should be a tag on your rear diff cover at the 9*clock position held on by the diff cover bolts. The gear ratio "(if they are stock/unchanged)". will be on the tag.
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Old 08-25-2009, 06:00 PM   #4
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This is a picture of a rear D35 but shows you the location of the tag....

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Old 08-26-2009, 08:01 AM   #5
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Yea those are both good explainations. I'll have to check tonight when I get home if there is a tag on the diff. So essentially, the lower the gear ratio the easier it is to spin larger tires?? As if you had larger tires and running stock gears the engine would be working harder to spin the tires?

thanks
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Old 08-26-2009, 11:38 AM   #6
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Yep, pretty much bud.

But remember numerally higher number in gears is actually lower.

I.E...4.10 gears are lower than 3.07 gears.
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Old 08-26-2009, 03:53 PM   #7
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So let's say you have 4.10 gears right now with stock wheels. What if you jumped up to a 33" tire, is it still a 4.10 gear or will that change?

I understand what you mean about the higher the gear the harder the engine works, that's all making sense now I'm digging an even further hole!
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Old 08-26-2009, 04:07 PM   #8
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Gears- if you go 33's on 4.10s it will feel as if you have 3.07's and stock tires. It will be sluggish until you get get moving 25-30. Right now I am running 33's and 5.13's with my 4 cyl. It drives extremely nice, and never do I really feel a lack of power anymore. What do you have for trannys? Since the manual and autos are geared differently. IF it a auto I would say 4.56's. If it is a manual go 4.88's and you will be extremely happy and since you have the dana 30 front the biggest gear you can go is 4.88's.

To the engine working harder- yes and no you will have to push on the gas a littler further with 4.10's and 33's. With 4.56's or 4.88's it will actually be a little faster. Faster as in will be able to get out of it's own way.
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Old 08-26-2009, 04:08 PM   #9
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Quote:
Originally Posted by Jeepn13 View Post
So let's say you have 4.10 gears right now with stock wheels. What if you jumped up to a 33" tire, is it still a 4.10 gear or will that change?

I understand what you mean about the higher the gear the harder the engine works, that's all making sense now I'm digging an even further hole!
Changing the tire size does not change the axle ratio which is also known as the ring & pinion gear ratio.

The axle ratio is the ratio of gear teeth between the pinion gear connected to the driveshaft and the ring gear connected to the axle shafts/wheels. So when the pinion gear (and driveshaft and engine) turns 4.10 times and the axle shaft/tire turns 1 time, that gives you a 4.10:1 (or more commonly called 4.10) ratio.

And if you see others refer to the ratio as a 4.11, that is correct too since our front and rear axles are slightly different so they often have about a .01 ratio difference between them which is inconsequential both on and offroad.
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Old 08-26-2009, 04:36 PM   #10
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Jeepin13...There is a lot to consider with combinations of rear end gears... tires sizes...engine torque...idea RPM ranges ..etc Here is a calculator to play with that may help with the big picture a little better:

Calculate Rear End Gear Ratio needed

Play with different tire sizes...desired RPM or MPH and see what happens to the require rear gear to keep things where you want them. Remember the calculator assumes you have the transmission in top gear at a 'one to one ratio'...not in a lower gear or in a vehicle with overdrive....

For a starting point...take you TJ out today and run it at 60mph in top gear...check the rpm at that speed...record your existing tire size and plug them it into the calculator....it should give you the ratio ( or very near it) marked on you rear diff. From there start playing with the varibles and see what you learn...have fun

Bill J




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Old 08-26-2009, 05:13 PM   #11
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Specbill not to knock your calculator but the best one I have found on the internet is this one.
Gear Ratio Calculator

This makes you plug everything in and on my truck it is dead on with what I have. You have to enter in the tranny you have, gear ratio, tire size. transfer case. It will give you all the info you need for everything you have.
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Old 08-27-2009, 08:37 AM   #12
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Now as far as figuring out what tranny and transfer case I have are they stamped somewhere too? I meant to check the rear diff last night, but never got a chance.... getting in at 2am didn't help the situation!!

thanks
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Old 08-27-2009, 05:08 PM   #13
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Quote:
Originally Posted by Jeepn13 View Post
Now as far as figuring out what tranny and transfer case I have are they stamped somewhere too? I meant to check the rear diff last night, but never got a chance.... getting in at 2am didn't help the situation!!

thanks
4cyl or 6cyl....auto or manual??

I can tell you what trans you have.

Your t-case is a 231.
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Old 08-28-2009, 07:39 AM   #14
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It's an 04 Sahara 6cyl manual. Now as far as the transfer case is a 231 common?
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Old 08-28-2009, 08:51 AM   #15
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Quote:
Originally Posted by Jeepn13 View Post
It's an 04 Sahara 6cyl manual. Now as far as the transfer case is a 231 common?
231j is Standard on ALL TJ's with the exception of to rubicon model.

2004 5speed manual = NV3550 ----
* Used with 6 cyl models
* 10 spline input
* 23 spline output
* Ratios:
1st - 4.01
2nd - 2.33
3rd - 1.39
4th - 1.00
5th - 0.78
Rev - 3.57

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Old 02-02-2014, 04:04 AM   #16
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Hi All, neebie to the jeep world here, but long time 4wder.

I'm trying to find out a bit more about the dana 30 44 diffs. I've just bought a TJ with the 30 44 combo but i'm just about positive it has 3.07 gears in it. Most sites ive looked at say that i can only go upto a 3.73 ratio when going from 3.07.
Is this because of the ring gear carrier cant fit the smaller 3.73 or higher ring gear on it?
If i change the carrier housing to the smaller one can i then put 3.73 and higher gears into the dana 30.

The TJ i bought already has 3 1/2" lift with 4 link front and rear hi flex conversion with 33's on it. I'm wanting to change the gears to at least 4.56 maybe even 4.88.
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Old 02-02-2014, 10:22 AM   #17
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I am pretty sure the stock gear ratios for the D44 is 3.73. And according to a post earlier in this thread, the numerically highest gear ratio you can go in a D30 is 4.88.
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Old 02-02-2014, 12:28 PM   #18
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In the U.S. all non-Rubicon Wranglers with a Dana 44 in the rear have a 3.73 ratio. And yep, 4.88 is as low of a ratio as can be installed into the front Dana 30 though the Dana 44 can be geared lower than 4.88.

But no telling what ratio gets exported to Australia with the export version of the Wrangler. Probably 3.73 but export versions aren't always the same as what we get here in the U.S. I'd guess it'd be 3.73 though.
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Old 02-02-2014, 02:43 PM   #19
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Hi guys,

Please note, i'm from Aust not US, our wranglers are different combos to the US versions. Diff gears are definitely 3.07 (unfortunately).

But what i'm trying to find out is, Can i just go straight upto a 4.88 ratio or does the diff centre ring gear carrier housing need to be changed to accept the higher ratio of above 3.73?
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Old 02-02-2014, 04:54 PM   #20
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You will need new carriers for both the front and rear to go to 4.88 from your present 3.07.
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Old 02-02-2014, 06:37 PM   #21
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Ok no worries thats what i thought. Thanks.

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