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Old 07-14-2016, 12:47 AM   #1 (permalink)
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Newbie tries to understand gears

Hello! I'm looking to regear my 05 TJ d30/8.8 soon and would like some real world, first hand accounts of re-gearing with this specific set-up. It's a daily driver of city/highway with maybe 1-2 trips per year to the mountains and light trails.

How will 5.13 work with 31s, 33s, and 35s?

I have a d30 up front and soon to be 8.8 rear.
4.0 6cyl.
42RLE 4 speed auto (with the .69 OD)
np231 4:1? TC

I hear good things about 5.13 (or higher) with the auto, but mst of the shops I ask say no higher than 4.56, which I believe is more suited towards manuals. It's silly trying to explain why I might want 5.13 to some of them
Looking for the best mix of power and economy. Thanks!

Please don't flame me!!
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Old 07-14-2016, 01:24 AM   #2 (permalink)
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The lowest you can go with the 30 is 4.88. With 31s you will be turning a shit load of rpms,

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Old 07-14-2016, 03:05 AM   #3 (permalink)
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That may have been true in the past but there are certainly 5.13 r&p kits available for the Dana 30
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Old 07-14-2016, 03:59 AM   #4 (permalink)
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The shop is probably telling you 4.56 because if you go any lower there is not enough material on the ring to handle the torque. Look at pictures of 4.56 gears vs 4.88 gears and you will see a major difference in size.

Running tires that small you will not need to be that low. Most guys on 33s and 35s are running 4.10 or 4.56

Edit: also, I believe Dana 30 5.13 gears are only for the jk Dana 30s (07 and up) so you're still limited to 4.88

Last edited by will12785; 07-14-2016 at 04:02 AM.
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Old 07-14-2016, 06:56 AM   #5 (permalink)
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You can get 5.13 gears from revolution axle for the dana 30.
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Old 07-14-2016, 07:11 AM   #6 (permalink)
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The pinion head gets too small on 5.13's on the TJ dana 30. 5.13's will be way to low even with 35's. Also make sure what you are researching is for the TJ with the 4.0 and not for a JK with a gutless bottom ended minivan motor and overweight. Your 6cyl will have the low end power to not need extra low gears to still be drivable on and offroad.
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Old 07-14-2016, 07:12 AM   #7 (permalink)
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Go here Gear Ratio Calculator
And run some sims and crunch the numbers and you will get a better idea of what you want to get the RPM's you want/need.
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Old 07-14-2016, 08:09 AM   #8 (permalink)
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Thanks for the replies. I think the revolution 5.13 the pinion gear is the same size, but the ring gear is smaller.

Iv used grimmjeepers calculator but I'm a little confused on what rpms I'm actually looking for or what even all those numbers truly mean.
I think 2000-2500 is the range I want for 4th with OD?
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Old 07-14-2016, 08:25 AM   #9 (permalink)
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231 T-case has a 2.72 ratio, not 4-1 .

If you go numerically higher than 4.88 in a Dana 30 the pinion head will be so small you will barely be able to see it with the naked eye, and weak AF .

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Old 07-14-2016, 08:28 AM   #10 (permalink)
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I would want my cruise RPM to be right at or just before the engines peak torque for top gear at the legal limit in my state that will give optimum drive ability/mileage,
IMHO once you are back to that point you will be OK off road....at least for trails that you would run a rig that drives to the trail and if you plan to drive to the trail AND
run the harder trails it's time to add a under drive........$.02
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Old 07-14-2016, 10:50 AM   #11 (permalink)
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You need to pick a rpm for your final drive and gear to it,

You want 2500 but @ what mph?

The gear shop told you 4.56 because you told them "power and economy" well pick one or the other. 4.56 will keep your freeway rpm down, 5.13 will top you out @ 55mph. 4.56 wont go as slow off road.

If your 231 is stock its 2.61/2.72 not 4:1.
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Old 07-14-2016, 02:06 PM   #12 (permalink)
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I take it you have never seen the size difference between a d30 4.88 pinion and a factory 3.55? The 4.88 pinion is so small it's scary. There are tons of horror stories about guys breaking them off at the splines for the home be used of how small and weak that area is. 5.13 will be incredibly small. With that much gear and such small tires as a 33 or even a 35 you will probably be able to snap pinion gears on demand with a 4.0L
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Old 07-14-2016, 02:09 PM   #13 (permalink)
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Just remember one thing. Just because you can doesn't mean it's a good idea...
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Old 07-14-2016, 03:18 PM   #14 (permalink)
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Originally Posted by ranger4.0 View Post
I take it you have never seen the size difference between a d30 4.88 pinion and a factory 3.55? The 4.88 pinion is so small it's scary. There are tons of horror stories about guys breaking them off at the splines for the home be used of how small and weak that area is. 5.13 will be incredibly small. With that much gear and such small tires as a 33 or even a 35 you will probably be able to snap pinion gears on demand with a 4.0L
I know this is a popular debate with 5.13 in the past, however Revolutions 5.13 set for the d30 *claims* that they were able to achieve this by "changing the tooth count on the ring gear so the size of the pinion head size did not have to be sacrificed."

With that said, using the correct listing nv231 (not the nv231 w/ 4;1 mod which is directly after the stock one) I think I finally figured out how to read the GJ calculator!

With 33s:
5.13 @ 70 mph is ~2523 rpms in 4th (OD)
5.13 @ 55 mph is ~1982 rpms in 4th (OD)

With 33s:
4.88 @ 70mph is ~2400 rpms in 4th (OD)
4.88 @ 55mph is ~1886 rpms in 4th (OD)

With 33s:
4.56 @ 70 mph is ~2243 rpms in 4th (OD)
4.56 @ 55 mph is ~1762 rpms in 4th (OD)

If say I wanted to have a quick(er) off the line acceleration, would I look for a lower RPM range in 1st? Say like 1300-1400-1500 before the tranny shifts? I know i have to *pick one* between power and economy, i'm looking for a balance of both, or a sweet spot.
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Old 07-14-2016, 03:21 PM   #15 (permalink)
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The point I was trying to make is the fact that lower gearing like 5.13 will make it possible to put way more stress on the entire front axle assembly. Breaking u-Joints, snapping axles etc becomes a lot easier
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Old 07-14-2016, 05:34 PM   #16 (permalink)
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If you build the axle to work with the gearing there should be little to no problems... IMO
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Old 07-14-2016, 06:22 PM   #17 (permalink)
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No shit. So how much $$$ are you willing to spend to make a d30 live?

The difference from 5.13 - 4.56 is only 300 rpm for your hiway. With the 5.13 being much more likely to break or break something else....
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Old 07-15-2016, 03:21 AM   #18 (permalink)
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If you build the axle to work with the gearing there should be little to no problems... IMO
With gearing as deep as 5.13 and axle shafts as small as they are in a d30 it doesn't matter if you have chromo shafts, you have a much higher chance of breaking shit. There is a good reason no one has made 5.13 gears for a d30 until now. They also advertise being able to run 40s with this gear set. That is just fucking retarded for a d30. The only way I see there being "little to no problems" is if his jeep never left the damn garage
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Old 07-15-2016, 05:08 AM   #19 (permalink)
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Originally Posted by ranger4.0 View Post
They also advertise being able to run 40s with this gear set.

That's the stupidest thing I've read for a long time.

That is just fucking retarded for a d30.

Agreed




The only way I see there being "little to no problems" is if his jeep never left the damn garage

40's with a D30
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Old 07-15-2016, 07:46 AM   #20 (permalink)
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Quote:
Originally Posted by ranger4.0 View Post
They also advertise being able to run 40s with this gear set.

That's the stupidest thing I've read for a long time.

That is just fucking retarded for a d30.

Agreed




The only way I see there being "little to no problems" is if his jeep never left the damn garage

40's with a D30
Not that it matters to me, but it actually states you can conceivably run 40" on a Tj rubicon d44 with 5.38, not a d30 with 5.13.
5.13 is for the d30/d35 and probably capped at 33s/35s.

Regardless, I think I should just build the TJ for a mall crawl DD and just buy a jk/Jl for crawling
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Old 07-15-2016, 04:34 PM   #21 (permalink)
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I'm not trying to be a dick. Just trying to point out the chain of weak links both with the weak front axle and the idea of gears that deep. I hate watching people spend money on things like this and then realize they want bigger tires or more power and all that money spent was for nothing. Could have went into swapping a stronger axle that will live with everything else planned for the build
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Old 07-15-2016, 06:09 PM   #22 (permalink)
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Quote:
Originally Posted by ranger4.0 View Post
With gearing as deep as 5.13 and axle shafts as small as they are in a d30 it doesn't matter if you have chromo shafts, you have a much higher chance of breaking shit. There is a good reason no one has made 5.13 gears for a d30 until now. They also advertise being able to run 40s with this gear set. That is just fucking retarded for a d30. The only way I see there being "little to no problems" is if his jeep never left the damn garage
Your the first one to state running 40's. I was talking about the availability of gearing for a mild build and that sounds like what the OP is talking about.
A well built HPd30 will work well with 35" tires...
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Old 07-15-2016, 08:48 PM   #23 (permalink)
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Yes I agree a well built 30 will handle 35s. It's already been established I misread the website. They state 40s on a tj rubicon d44.
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Old 07-15-2016, 10:45 PM   #24 (permalink)
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Thanks for clarifying


I've been mulling over how temporary d30's on 40's would be, for a few hours today here.
Imagining a matched d35 rear with 40's would be fine with them too.

True story. Hahaha.

Last edited by 3nuts; 07-15-2016 at 10:46 PM.
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Old 07-15-2016, 11:32 PM   #25 (permalink)
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Originally Posted by ranger4.0 View Post
They state 40s on a tj rubicon d44.
Meh, not enough of a difference to matter. The outers are still the same and that's usually what breaks.
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