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Unread 02-05-2015, 07:14 AM   #1
monkey6
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3.7 rear axle swap

I've seen a lot of people on here mention swapping the rear axle of the 3.7 and installing the 12 bolt with the electronic locker, but I can't find anywhere that someone has actually attempted this. I am highly interested in doing the swap on my WK, but have a few questions.

Are there any sensors on the stock axle that will have issues once it is swapped? (engine codes or EVIC messages?)

Is the gear ratio the same on the different axles? And if it is different, will it affect the jeep having a different rear ratio and not changing the front?

I don't know if anyone has actually done this, but I plan on attempting it in the near future if I can find a new axle at a junk yard in good condition. I plan on wiring a switch to manually engage the electronic locker. I also have the Hypertech tuner which should allow me to reprogram the gear ratio if necessary.

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Unread 02-05-2015, 08:03 AM   #2
JeepN4KC
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This topic is all show and no go because it is far more involved than simply swapping the rear axle.

The gearing in the 3.7 is 3.07 vs 3.73 in the QDII axles - this would require regearing or swapping the front axle as well.

The limited slip in the QDII is electronic which would be quite involved to establish.

W/o a low gearing transfer case having ELSDs is pointless in my book.

Long story short - the swap would not be worth the time or money.
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Unread 02-05-2015, 10:36 AM   #3
luckyse7ens
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Quote:
Originally Posted by JeepN4KC View Post
This topic is all show and no go because it is far more involved than simply swapping the rear axle.

The gearing in the 3.7 is 3.07 vs 3.73 in the QDII axles - this would require regearing or swapping the front axle as well.

The limited slip in the QDII is electronic which would be quite involved to establish.

W/o a low gearing transfer case having ELSDs is pointless in my book.

Long story short - the swap would not be worth the time or money.
3.73's and ELSD would make a 2wd Jeep much more capable. Even without the xfer case. Would be worthwhile if the rear was on its way out already.

Any reason why the locker couldn't just be wired to a switch?

"worth the time and money" is certainly up to the end user. I could see a front diff gear swap + rear qd2 diff being reasonable if you can do a JY pull and are capable of doing your own work.
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Unread 02-05-2015, 10:41 AM   #4
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Why not throw an aussie locker in your stock rearend?
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Unread 02-05-2015, 10:42 AM   #5
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Quote:
Originally Posted by luckyse7ens View Post
3.73's and ELSD would make a 2wd Jeep much more capable. Even without the xfer case. Would be worthwhile if the rear was on its way out already.

Any reason why the locker couldn't just be wired to a switch?

"worth the time and money" is certainly up to the end user. I could see a front diff gear swap + rear qd2 diff being reasonable if you can do a JY pull and are capable of doing your own work.
Right, and if you have the resources, time, and money to be making all these axle swaps and regearing - then the WK is the wrong platform to be performing them on IMO.

As an example, couple grand gets you a decent XJ, or even ZJ base to work from vs. several more thousand to get the WK base to work off of.
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Unread 02-05-2015, 10:44 AM   #6
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Originally Posted by JeepN4KC View Post
Right, and if you have the resources, time, and money to be making all these axle swaps and regearing - then the WK is the wrong platform to be performing them on IMO.

As an example, couple grand gets you a decent XJ, or even ZJ base to work from vs. several more thousand to get the WK base to work off of.
Oh I hear that. Some people just like playing with more expensive toys.
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Unread 02-05-2015, 11:05 AM   #7
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My advice is leave the 3.7 as it is. No low range makes gearing and lockers quite useless for offroading.

If you actually want to dump money into it, which is not worth it IMO, then do a QT2 swap, regear to 4:10's, and get ARB selectable lockers.
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Unread 02-05-2015, 11:25 AM   #8
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I dont think its as crazy of an idea as some of these guys. Haha. It's pretty simple to manually actuate the elsd via switches.

You can even find the axles on ebaymotors pretty decently priced out of wrecked wks. I toyed with the idea of going to 3.07s in my crd but just dont have the funds, but used axles werent that uncommon when i was looking.

If it was 2wd its really simple. For a 4wd its more work since you have to swap front and rear but still should be pretty straightforward in my head.

If youre into off roading not having 4lo will limit you, but even just having lockers front and rear would be night and day over stock.
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Unread 02-05-2015, 11:39 AM   #9
monkey6
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Quote:
Originally Posted by Hendrix9 View Post
If youre into off roading not having 4lo will limit you, but even just having lockers front and rear would be night and day over stock.
Exactly, I really just want to have the locker for comfort, I don't do anything extreme enough that 4low would be limiting me. I've gone through a small stream that was in a steep valley. I was uncomfortable going slow without a locker because if I got a wheel off the ground I'd be screwed, so I took a little faster so momentum would pull me through the rough spots. Is it possible to install any type of locker in the 10 bolt diff without doing a swap? I thought I read somewhere that there isn't enough room in there.
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Unread 02-05-2015, 12:23 PM   #10
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Quote:
Originally Posted by modernblueWK View Post
Why not throw an aussie locker in your stock rearend?
Quote:
Originally Posted by monkey6 View Post
Exactly, I really just want to have the locker for comfort, I don't do anything extreme enough that 4low would be limiting me. I've gone through a small stream that was in a steep valley. I was uncomfortable going slow without a locker because if I got a wheel off the ground I'd be screwed, so I took a little faster so momentum would pull me through the rough spots. Is it possible to install any type of locker in the 10 bolt diff without doing a swap? I thought I read somewhere that there isn't enough room in there.
Then do as mentioned above and put a lunchbox locker in the rear.

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Unread 02-05-2015, 12:25 PM   #11
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I believe Powertrax makes something for the 8.25" 10 bolt rear end. I can't remember which model it is though. They have a few to choose from. Just check out their site.

The 2wd WKs and XKs come with a Dana rear end. There's all sorts of options for that rear end.

But it is possible to put in the front and rear ESLD axles and wire the solenoid up to a switch. I believe you'd lose the limited slip aspect of it, but you can use the switch to fully lock it. You'd probably have to work closely with the dealer though to reprogram the PCM for the different gear ratio.
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Unread 02-05-2015, 12:28 PM   #12
JeepN4KC
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AFAIK all those brands I listed make a locker to fit the carrier of the 29 spline C8.25
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Unread 02-05-2015, 12:35 PM   #13
monkey6
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Quote:
Originally Posted by JeepN4KC View Post
AFAIK all those brands I listed make a locker to fit the carrier of the 29 spline C8.25
Awesome, I'll have to do some more research on that!
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Unread 02-08-2015, 10:30 AM   #14
jeepin_in_a_wk
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i AM actually going to be tackling this project, qd2 axles in a qt1. im running the modded ome with 265/70/17, plus custom front and rear bumpers in the next few weeks, so i really need the 3.73 gears to help me out. i will make a thread when i start it and update along the way
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Unread 02-08-2015, 10:43 AM   #15
modernblueWK
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So have you looked into what computer programming you will need to do to make it work? Can a superchips program the computer for 3.73's?

I thought the limited slip aspect on qd2 was mechanical and the full lockup was electrical.
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