Basic Re-Gearing Advice (to 4.10)

Oban · **Joined:** Sun Apr 06, 2014 2:48 pm **Posts:** 64

Good evening!

I searched the forum and did some research on google. Here is what I believe I gathered so far is true for our KK's:

- Rear axle is a Chrysler Corp 8.25
- Front is a Dana 30.

To re-gear I would need to buy the following:

- Master Rebuild Kit for Chrysler 8.25 Rear
- 4.10 Rear Gears (several manufacturers available)
- Master Rebuild Kit for Dana 30a Front
- 4.10 Front Gears (apparently only available manufacturer is Dana???)

I also gathered from various threads that this is not a DIY job and requires experience and tools not everybody has, such as a press.

Does this sound right so far?

Edit / Note: as clarified in the posts below, my understanding of the KK having a Dana 30a was wrong. It is in fact a Dana 30.

I found the rebuild kit for the 8.25 on various websites. I also found the rear gears - Yukon is one example. What I am struggling with is the front. Each time I search for Dana 30a I find a ton of stuff for the Dana 30. However, not the 30a!

I already found a reputable shop in the Chicago area that would do the install, but I prefer to source my own parts based on the experience of other users here at Lost.

Is there by chance a part number for the front (rebuild kit and gears)? I found various shopping lists here and at other forums, but it was a mix of Wranglers, Liberty KJ's and whatnot. I also read several warnings that Dana 30 doesn't fit Dana 30a. So any help identifying the proper parts would be appreciated.

As for why I want to re-gear: I currently run larger tires on an OME lift. I just want the KK to have better low RPM torque and power. It feels sluggish every now and then, especially during long drives in mountain areas. Plus, the never ending hunt for gears by the tranny is simply annoying.

Any additional advice is greatly welcome.

tommudd · **Posted:** Mon Jul 06, 2015 7:35 am

KKs DO NOT have a D30a, they have a regular 30 like in a JK Sport , lower trim levels
rear is the same KJ or KK

lfhoward · **Posted:** Mon Jul 06, 2015 8:46 am

Tom is correct. The KJ Liberty has the Dana 30a up front, but our KK's have the 30 and use the same gears as the JK Wrangler with that diff. I have done some research on gears as I want to go to 4.10s eventually too. You can search for 4.10 gears and rebuild kits for JK (2007+) Wranglers on the gear websites and find lots of choices.

Oban · **Joined:** Sun Apr 06, 2014 2:48 pm **Posts:** 64

I am glad I asked!

Thanks for clarifying. I have modified my original post to reflect that the KK has a Dana 30, NOT 30a.

You made my life heck of a lot easier.

Bmxer524 · **Posted:** Mon Jul 06, 2015 11:21 am

They basically said it. Front is a Dana 30. It uses the same gears as 07-present(and assumingly 2016) Wranglers (JK/JKU) Sports and Saharas. Rear is a Chrysler 8.25, I don't think the spline count matters.

The main reason a lot of people go to pros for gears is because it requires a skill and patience that a lot of people don't have. For example, my family has been working on cars and boats for years. I've been taught everything by my dad and grandpa and none of us will touch a tranny or diff gears. But if you drop an engine in front of us and we'll have no problem rebuilding it for you. There's just too much you can mess up by just being of a hundredth of an inch.

Oban · **Joined:** Sun Apr 06, 2014 2:48 pm **Posts:** 64

Bmxer524 wrote:

The main reason a lot of people go to pros for gears is because it requires a skill and patience that a lot of people don't have. For example, my family has been working on cars and boats for years. I've been taught everything by my dad and grandpa and none of us will touch a tranny or diff gears. But if you drop an engine in front of us and we'll have no problem rebuilding it for you. There's just too much you can mess up by just being of a hundredth of an inch.

Agreed.

This is why I am saying that I will have a professional do it. I am not here to reinvent the wheel or claim that without experience I will figure it out. Screwing it up will cost too much in the end. I am simply interested in sourcing the parts myself and have a professional do the install / setup.

Oban · **Joined:** Sun Apr 06, 2014 2:48 pm **Posts:** 64

Just to verify with the experts here:

I found the following based on your input above. Both are 4.11 ratio.

REAR: Yukon (YG C8.25-411). However, it states 1976-2004 Chrysler 8.25" rearend (10 bolt rear cover). For the life of mine, I cannot find one for the 2005+ Chrysler 8.25 axle. Is there a difference?

FRONT: Yukon, Dana 30 Short Reverse Pinion (07-15 Wrangler JK Non-Rubicon; YG D30SR-411JK).

Would these work?

ajohns1288 · **Posted:** Mon Jul 06, 2015 9:04 pm

tommudd wrote:

KKs DO NOT have a D30a, they have a regular 30 like in a JK Sport , lower trim levels
rear is the same KJ or KK

I wish mine had a D30 from a JK, would make it a lot easier to swap in a 44. :mrgreen:

Info like this is what makes this place awesome. So what's the difference between the D30a and D30? The D30a is aluminum housing and special gears I take it?

Oban wrote:

Just to verify with the experts here:

I found the following based on your input above. Both are 4.11 ratio.

REAR: Yukon (YG C8.25-411). However, it states 1976-2004 Chrysler 8.25" rearend (10 bolt rear cover). For the life of mine, I cannot find one for the 2005+ Chrysler 8.25 axle. Is there a difference?

FRONT: Yukon, Dana 30 Short Reverse Pinion (07-15 Wrangler JK Non-Rubicon; YG D30SR-411JK).

Would these work?

I know there are 27 and 29 splines for the 8.25, but I would think the R&P would be the same. Based on this site I'd assume it would work as it lists the Nitro (our ugly sister) as compatable: https://www.yukongear.com/DiffDetails.a ... 2797-%2704

JeepMorrison · **Joined:** Thu Jul 16, 2009 11:34 am **Posts:** 1236

ajohns1288 wrote:

tommudd wrote:

KKs DO NOT have a D30a, they have a regular 30 like in a JK Sport , lower trim levels
rear is the same KJ or KK

I wish mine had a D30 from a JK, would make it a lot easier to swap in a 44. :mrgreen:

Info like this is what makes this place awesome. So what's the difference between the D30a and D30? The D30a is aluminum housing and special gears I take it?

Oban wrote:

Just to verify with the experts here:

I found the following based on your input above. Both are 4.11 ratio.

REAR: Yukon (YG C8.25-411). However, it states 1976-2004 Chrysler 8.25" rearend (10 bolt rear cover). For the life of mine, I cannot find one for the 2005+ Chrysler 8.25 axle. Is there a difference?

FRONT: Yukon, Dana 30 Short Reverse Pinion (07-15 Wrangler JK Non-Rubicon; YG D30SR-411JK).

Would these work?

I know there are 27 and 29 splines for the 8.25, but I would think the R&P would be the same. Based on this site I'd assume it would work as it lists the Nitro (our ugly sister) as compatable: https://www.yukongear.com/DiffDetails.a ... 2797-%2704

Not a easy swap, as you still have to cut it down and crap.

Both the KJ d30a and KKd30 is aluminum

Oban · **Joined:** Sun Apr 06, 2014 2:48 pm **Posts:** 64

So now I am more confused in terms of splines, etc.

Is there somewhere a past post / list with part numbers that would simply work for the KK? I don't want to cut anything down or modify. I simply want to buy new gears, hand them to my shop and have them install it. Ideally 4.10 or 4.11. Is there no direct fit out there?

tommudd · **Posted:** Tue Jul 07, 2015 5:06 pm

Oban wrote:

So now I am more confused in terms of splines, etc.

Is there somewhere a past post / list with part numbers that would simply work for the KK? I don't want to cut anything down or modify. I simply want to buy new gears, hand them to my shop and have them install it. Ideally 4.10 or 4.11. Is there no direct fit out there?

4.10 gears and install kit for a 8.25 rear diff with 29 spline in case that comes up
from same as a D30 on a JK easy to find

NAMoulton1 · **Joined:** Tue Aug 12, 2014 7:01 pm **Posts:** 1054

Here's Yukon install kits:

Front Axle: BK D30-JK http://www.amazon.com/gp/product/B0078U ... ge_o01_s00

Rear Axle: BK C8.25-B http://www.amazon.com/gp/product/B0078U ... ge_o00_s00

I regeared to 4.56s so I'm unsure of what and where to get the gears themselves. Although, the YG C8.25-411 that you showed do not fit the KK. I'm unsure as to what make them non-compatible though. There's other brands out there to get 4.10s from though.

Oban · **Joined:** Sun Apr 06, 2014 2:48 pm **Posts:** 64

I am close to giving up on this. Non of the websites seems to have either complete or non-contradicting information.

I read up on the 27 vs 29 splines, and it appears that the Corp 8.25 axle after 1999/2000 (or around that time) got the 29 splines. Everything prior was 27. At least based on what I read about stories concerning the XJ. :furious:

So then I looked at various online stores. Some tell me that the Yukon part number YG C8.25-411 should fit 2000+ 8.25 axles, which would be 29 splines. Other websites list the part with 27 splines under the same part number, which would mean that it wouldn't fit. Other list the Dodge Nitro as compatible until 2011, and the Liberty only until 2004. Other don't list the Liberty at all.

I then looked for different manufacturers. Some of which seem no-name and judging by the prices must be low quality China made stuff... so that is a no go.

So for the rear axle: still confused, can't find s$%t that seems to fit. :furious:

In my frustration I turned to the front axle and found the Yukon YG_D30SR-411JK here: http://www.ringpinion.com/b2c/ProductDetails.aspx?ProdID=12188&Product=YG_D30SR-411JK&Brand=Yukon_Gear_Ring_and_Pinion_Sets

It clearly lists the Jeep JK non-Rubicon (2007 - 2015) Dana 30 as a fit, but it also says it is a "short reverse Pinion", which I have not heard of or read about in any of the Liberty KK boards. So again, not sure it will fit.

I mean, come on, what have you guys purchased? I am at a point where I almost don't care whether its 4.10, 4.11 or 4.56. At least on the 4.56's it seems I'd be able to get some solid advice as to what folks have previously purchased for their KK's and which worked out to fit...

I see so many KK's on the road here in Illinois every day. I wish the aftermarket wouldn't hate us so much. :banghead:

Usually I am firm believer in reading and trying to figure this out, but with these gears it just simply doesn't add up. I'd even be willing to take my diff's apart and measure the components, but the supplier websites don't even offer technical / dimensional drawings for any of their products. It is a pain.

Thoughts?

NAMoulton1 · **Joined:** Tue Aug 12, 2014 7:01 pm **Posts:** 1054

I went through the same frustration figuring out my 4.56s. Thankfully managed to find Yukon everything. You should be able to find 4.10s from another company pretty easily. Just don't over complicate it. Be patient with it and go to the shop with ALL the information before you even go in. Doesn't matter the reputation of a shop, they're morons when they work on the KKs hahaha.

On a side note, it's sometimes better to give the part numbers to the shop for them to purchase because then you can eligible for awesome warraties. Like mine for instance, because the shop was a certified Yukon dealer and installer, I got an insurance from them that's awesome. It's free replacements if they break plus $2000 collateral damage in case the screwed up gears destroy the axle. Worth it for the piece of mind haha.

tjkj2002 · **Posted:** Wed Jul 08, 2015 11:34 pm

The KK uses a D30M front diff.The '06+ 8.25's have some differences that make older gear sets not work compared to older 8.25's.

JeepMorrison · **Joined:** Thu Jul 16, 2009 11:34 am **Posts:** 1236

tjkj2002 wrote:

The KK uses a D30M front diff.The '06+ 8.25's have some differences that make older gear sets not work compared to older 8.25's.

OMG i have been trying to tell people this on Facebookhell....they dont listen

PALiftedKK · **Posted:** Fri Jul 17, 2015 6:56 am

I will be saving this topic to when I regear and throw in lockers!

Still a big fan of OX.

I do not want an e locker at all! Air or electronic locker is preference.

^ though still on the fence if the KK is a 27 or a 29 spline. 95% sure its a 29 though.

tommudd · **Posted:** Fri Jul 17, 2015 10:51 am

4x4kayak2112 wrote:

tjkj2002 wrote:

The KK uses a D30M front diff.The '06+ 8.25's have some differences that make older gear sets not work compared to older 8.25's.

OMG i have been trying to tell people this on Facebookhell....they dont listen

Do any of them on Facebook listen?? :banghead:

tommudd · **Posted:** Fri Jul 17, 2015 10:53 am

PALiftedKK wrote:

I will be saving this topic to when I regear and throw in lockers!

Still a big fan of OX.

I do not want an e locker at all! Air or electronic locker is preference.

^ though still on the fence if the KK is a 27 or a 29 spline. 95% sure its a 29 though.

still on the fence??? Why , many many posts explaining the 8.25 is 29

JeepMorrison · **Joined:** Thu Jul 16, 2009 11:34 am **Posts:** 1236

tommudd wrote:

PALiftedKK wrote:

I will be saving this topic to when I regear and throw in lockers!

Still a big fan of OX.

I do not want an e locker at all! Air or electronic locker is preference.

^ though still on the fence if the KK is a 27 or a 29 spline. 95% sure its a 29 though.

still on the fence??? Why , many many posts explaining the 8.25 is 29

OX has what you need.....i have their 8.25 and d30 lockers, and my buddy has the OX in his JKd30.

Basic Re-Gearing Advice (to 4.10)

Who is online