Gear ratio

[1BADKJ]

What is the lowest gear ratio I can put in my front diff.

 

[WickedBruce]

4.10

 

[1BADKJ]

4.10

****!!!!!! So even if I change the carrier I can only use 4.10s

 

[WickedBruce]

U can get the jba steel diff...

 

[1BADKJ]

U can get the jba steel diff...

Hell no. This lift is only a temp. Doing SFA So even if I change my carrier I can only do 4.10s

 

[WickedBruce]

As far as I know, yes

 

[tjkj2002]

Hell no. This lift is only a temp. Doing SFA So even if I change my carrier I can only do 4.10s

No carrier break for the D30A,only 3 gear sets made for the D30A anyways.

3.55's
3.73's
4.10's

 

[The Big Boulonnais]

Any alternative to the JBA steel diff ?

No carrier break for the D30A,only 3 gear sets made for the D30A anyways.

3.55's
3.73's
4.10's

Hi guys,

Like lots of people I would like to upgrade from 31" to 33" but the gear ratio has got to change to at least 4.56 or even better 4.88 but as TJKJ mentioned above 4.10 is the Higher gear set made for the D30A and for the Chrysler 8.25" fitted in KJ from 2005 to 2007 I believe.

So I would like to know if there is a cheaper alternative to the JBA steel diff which I believe is a Dana 30. Would a steel Dana 30 coming from another model of Jeep from a scrap yard do the job? I mean of course fitting afterwards the right pinion & gear set.

And what about a Chrystler 8.25" from an XJ 97 to 2001? Would this diff fit with the axles of a KJ ?

 

[tjkj2002]

Hi guys,

Like lots of people I would like to upgrade from 31" to 33" but the gear ratio has got to change to at least 4.56 or even better 4.88 but as TJKJ mentioned above 4.10 is the Higher gear set made for the D30A and for the Chrysler 8.25" fitted in KJ from 2005 to 2007 I believe.

So I would like to know if there is a cheaper alternative to the JBA steel diff which I believe is a Dana 30. Would a steel Dana 30 coming from another model of Jeep from a scrap yard do the job? I mean of course fitting afterwards the right pinion & gear set.

And what about a Chrystler 8.25" from an XJ 97 to 2001? Would this diff fit with the axles of a KJ ?

JBA's steel diff is a cut down D30 modified to work on a IFS KJ to retain IFS and regear lower.Besides getting the JBA steel diff your only otherway is to do a SFA conversion,eitherway the stock D30A will not last long with 33" tires.

The 8.25 in any year of the KJ,and KK,uses the same gears so be it a '02 KJ with the 8.25 or a '12 KK with the 8.25 you can regear to 4.56's.There are 4.88's out there but you must grind down some of the ring gears teeth to get the center pin back in.A 8.25 from a XJ is narrower then a KJ's and you'd have to weld on new mounts to bolt into the KJ,but it is narrower so no KJ 8.25 axle shafts will not work in a XJ's 8.25.Some XJ's 8.25's are 27 spline also.

 

[The Big Boulonnais]

JBA's steel diff is a cut down D30 modified to work on a IFS KJ to retain IFS and regear lower.Besides getting the JBA steel diff your only otherway is to do a SFA conversion,eitherway the stock D30A will not last long with 33" tires.

The 8.25 in any year of the KJ,and KK,uses the same gears so be it a '02 KJ with the 8.25 or a '12 KK with the 8.25 you can regear to 4.56's.There are 4.88's out there but you must grind down some of the ring gears teeth to get the center pin back in.A 8.25 from a XJ is narrower then a KJ's and you'd have to weld on new mounts to bolt into the KJ,but it is narrower so no KJ 8.25 axle shafts will not work in a XJ's 8.25.Some XJ's 8.25's are 27 spline also.

Thanks for the info about the JBA steel diff it seems that is the only way to fit 4.56 ratio with an IFS then.

I am now in the Yukon website and they show 2 models of Chrysler 8.25".
The one used on Liberty 2005 to 2013 (C213R/C213RE) they make only one Ring & pinion gear set in a 3.55 ratio.
The other Chrysler 8.25" used on Liberty 2002 to 2004 and XJ 97 to 2001 has 6 Ring & pinion gear set ratios from 2.76 to 4.88.

I have a KJ CRD 2006 so this is why I was asking the question about a Diff coming from an XJ. Sorry if I am wrong here I was relying on Yukon info.

 

[tommudd]

Some of those sites never did get the Liberty info right, even after all of these years

 

[LibertyFever]

Isn't it stamped into the carriers? The next time you have your diff cover off you can look for it.

sent from my Galaxy SIII & Tapatalk4 beta

 

[The Big Boulonnais]

Some of those sites never did get the Liberty info right, even after all of these years

Yes that's really amazing as they are THE Specialist. And they supply 2 different pictures of 8.25" Differentials.

If we can't rely of what Yukon says about differentials ..... who can we trust?

 

[tjkj2002]

Yes that's really amazing as they are THE Specialist. And they supply 2 different pictures of 8.25" Differentials.

If we can't rely of what Yukon says about differentials ..... who can we trust?

There are 2 versions of the 8.25,one version is the normal 30+ year old version(what you have) and the other is the bastard stepchild used in only the WK's that have that stupid ELSD.The diff you have is the narrow looking one as the other version is much wider(center section that is) to allow room for the actuator.

 

[The Big Boulonnais]

There are 2 versions of the 8.25,one version is the normal 30+ year old version(what you have) and the other is the bastard stepchild used in only the WK's that have that stupid ELSD.The diff you have is the narrow looking one as the other version is much wider(center section that is) to allow room for the actuator.

Thanks TJKJ, Now that makes sense !! And I am glad to know that I could go up to 4.56 ratio in my own diff. I was going to have an ARB Air locker fitted in the rear so I thought I might as well re-gear.

The big dilemma I have now is that I am only at 22" between wheel hub and fender at front and rear but I've had some serious trimming done already to accommodate the 31" M. Thompson Baja so it looks like I wouldn't have too much to do to fit 33" tyres with no rubbing. If I could find a pair of old 33x10.5x15 I would try to see if it's possible to do the work or not.
If 33"s could fit I would buy the JBA steel D30 with 4.56 pinions ratio for front & rear. If I couldn't fit the 33"s then I would stick to 31"s and keep my front D30A and re-gear with 4.10. That would improve things anyway as I am still at 3.73 at the moment.

Let me know what you think about this, please. I know you ride on 35"s but your KJ is fitted with SFA and God knows how tall is your lift. Lol

 

[tjkj2002]

You will need to be well over 23" flare to hub,more like closer to 24"-25"(5"-6" of lift) to clear 33" tires and still maintain full flex.


I'm at 9" of lift to get full flex while running 35" tires with full width axles(5" wider then stock).

 

[colorado76]

My question, is for those of you that have regeared to 4.10 do you get more power when climbing up passes? Because I'm running 31's and don't have much power and just really want to know if it's worth the time and money to regear my KJ.

 

[yellocoyote]

Yes.

How much power seems to be relative to which transmission you have. I've seen posts all day long where people with the 42RLE who have regeared to 4.10's sing the praises of how much power they got back with their regear...

While those of us rocking the 45RFE experience power increases, yes... but it's not the striking difference that the others seem to have.

 

[colorado76]

Thanks, for the input Yellocoyote.

 

[The Big Boulonnais]

Yes.

How much power seems to be relative to which transmission you have. I've seen posts all day long where people with the 42RLE who have regeared to 4.10's sing the praises of how much power they got back with their regear...

While those of us rocking the 45RFE experience power increases, yes... but it's not the striking difference that the others seem to have.

Any idea about the effect of 4.10 ratio with 31"s tyres for the NSG370 6-speed overdrive manual transmission ? As it's what I've got fitted on my 2.8CRD.