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Rear Axle Swap, Technical help needed


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Hello, i am new to this club, and i have a Comanche with a Dana 350 rear axle in it. I was looking to upgrade to a different rear axle with disk brakes and maybe a 3.73 gear ratio, limited slip/clutch drive rear differential. Do you know possibly what year Cherokee or what vehicle i could pull something like this out of or where i could order something like this? possibly as a complete assembly with springs and all? If anyone could help it would be much appreciated.

 

Keep it Crawlin and keep it Rockin :banana:

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Cole - I think you mean a Dana 35.   A Dana 350 would be HUGE!  :laugh:  Rear disc brakes from a Jeep Liberty are basically a straight bolt on.   Older Grand Cherokee brakes work too with minor work done to the backing plates.    I don't know if 3.73 gears are year specific but they do exist.   I'm sure someone else can chime in on that.    

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What is your budget?

 

Lots of money, least amount of hassle, I'd say phone Currie, Dynatrac, etc and have them build you a D44, 9", or whatever that meets your specs.  They can sell you a brand new bolt in axle.  It will not be cheap, but all the parts will be new and it will be a nice product.

 

Not so much money, a guy could find a MJ D44 and do a brake conversion on it.  The 3.73 ratio is quite rare though, I'm not sure what option package would yield that, if any (4L trucks are always 3.07 or 3.55), so if you really want 3.73s you would have to plan on a gear swap, and you might as well put a Truetrac limited slip in at the same time.  Plus all new bearings.  This wouldn't be a super cheap swap by any means, I've got a couple thousand bucks into my rear D44 all said and done.

 

I thick the cheapest option would be an Explorer 8.8 as 3.73 and 4.10 were the two common ratios, and it's easy to get them with a clutch pack limited slip, and the later ones are all disk brake from the factory.  You would need new perches welded on for the springs, don't forget the companion flange and bolts for the driveshaft, and you will need to do some finagling to adapt the ebrake cables.  It's a well built axle and they're very available used, but it does have the downside of being a bit narrow for the MJ, so a set of wheel spacers is a good idea with it.  There's also the way overblown problem of it spinning the tubes in the pumpkin, which is easy to correct by welding the tube perimeter when the perches are put on.  I farmed out the welding on my first 8.8 swap and I recall it only cost me the minimum charge in labour ($120) to have the perches and tubes welded, which was certainly worth it at the time, if you're unable to weld I would suggest doing the same thing.

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.....or an 8.25 out of a KJ.  Most of the 3.7L autos are 3.73 and some are LS.  2002 model year only (the first model year) they had drum brakes, but all after that were discs.  You'd need new perches and would have to rig up the e-brake cables, but the WMS is near perfect and you can keep the 5x4.5 bolt pattern.  Plus they're all 29 spline (unlike older XJ 8.25's which could be 27).

 

 

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Another vote for the 2003+ KJ rear. I have one with 3.73s and a limited slip. It makes a very good swap for the MJ and coming from a jeep that replaced the XJ makes it an easier swap in than some other options. 

 

I have a couple of videos videos showing the details of using this axle in an MJ. 

 

 

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87 to 95 Jeep YJs with automatic transmissions typically have 3.73 Dana 35s.  Nearly all 2.5L engines have that ratio with autos.  Most 4.0L engines with auto have them too, but sometimes 3.55 are in there.  YJ to MJ conversion requires moving the spring perches and cutting the track bar mount off.  ZJ discs bolt right on.  For c-clip axles no special tools are needed for the disc brake conversion.  It will be harder finding a decent 3.73 D30 front.  Look at TJs for that.  Good luck.

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53 minutes ago, kryptronic said:

87 to 95 Jeep YJs with automatic transmissions typically have 3.73 Dana 35s.  Nearly all 2.5L engines have that ratio with autos.  Most 4.0L engines with auto have them too, but sometimes 3.55 are in there.  YJ to MJ conversion requires moving the spring perches and cutting the track bar mount off.  ZJ discs bolt right on.  For c-clip axles no special tools are needed for the disc brake conversion.  It will be harder finding a decent 3.73 D30 front.  Look at TJs for that.  Good luck.

 

Actually most XJ were 4L and Aw4 auto. These all had 3.55s. 

 

4L and manual had 3.07s. 

 

I'm not sure I have ever come across an XJ with something other than that. But 4cyl XJs are so rare it's almost a moot point trying to find axles from a 4cyl. 

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I have a 1999 XJ with a police package that came from the factory with 3:73's.....it is the only time I have seen that ratio in an XJ......that being said if you are set on that ratio I would personally source the front first (as it is rare) then match it to a more easily attainable rear end ....IMHO

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4 hours ago, kryptronic said:

87 to 95 Jeep YJs with automatic transmissions typically have 3.73 Dana 35s.  Nearly all 2.5L engines have that ratio with autos.  Most 4.0L engines with auto have them too, but sometimes 3.55 are in there.  YJ to MJ conversion requires moving the spring perches and cutting the track bar mount off.  ZJ discs bolt right on.  For c-clip axles no special tools are needed for the disc brake conversion.  It will be harder finding a decent 3.73 D30 front.  Look at TJs for that.  Good luck.

 

If it's a D35 it doesn't really matter what ratio it is, it's a waste of time and money to swap it in.

 

28 minutes ago, yxmj said:

I have a 1999 XJ with a police package that came from the factory with 3:73's.....it is the only time I have seen that ratio in an XJ......that being said if you are set on that ratio I would personally source the front first (as it is rare) then match it to a more easily attainable rear end ....IMHO

 

Interesting, verified by checking the tags or gear stamps?   Must be special order.

 

23 minutes ago, Pete M said:

for a front axle, 3.73s are common in ZJs and TJs (as long as you're ok with a low pinion dana 30)

 

Low pinion front axles suck, I'd pay for a set of gears + setup before running one.

 

14 minutes ago, Minuit said:

I believe some early (very early) XJs could have 3.31s as well. I've heard some tow package XJs had 3.73s but never seen anything to back that up.

 

I think in 84-85 (and some extent 86) there is the potential for just about any freaking oddball part in the world to come bolted onto an AMC product, especially the XJ.  The tow package XJ 3.73 ratio appears to be a myth, but then again I've never seen a 3.73 ratio XJ axle period, 95% of them come with a 4L and they're always been 3.07 or 3.55.

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On 2/6/2018 at 1:20 PM, Cole2000x said:

Hello, i am new to this club, and i have a Comanche with a Dana 350 rear axle in it. I was looking to upgrade to a different rear axle with disk brakes and maybe a 3.73 gear ratio, limited slip/clutch drive rear differential. Do you know possibly what year Cherokee or what vehicle i could pull something like this out of or where i could order something like this? possibly as a complete assembly with springs and all? If anyone could help it would be much appreciated.

 

Getting back to the OP's original post:

 

Some good advice above but possibly irrelevant in parts until we know what you have and what your plans are. The following info needs to be provided:

 

What tire size do you plan on running?

Is this going to be a street vehicle primarily, or off-road, or both?

Are you 2WD or 4WD now, and what is your current gear ratio?

Transmission? Etc. etc. ......

 

Can't help effectively until we know at least this basic information. And it would be good if you created a signature so we know what you are driving. Here's how to do it:

 

https://comancheclub.com/forums/topic/51707-cc-members-create-a-signature-to-describe-your-mj/

 

 

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5 hours ago, Sir Sam said:

 

Actually most XJ were 4L and Aw4 auto. These all had 3.55s. 

 

4L and manual had 3.07s. 

 

I'm not sure I have ever come across an XJ with something other than that. But 4cyl XJs are so rare it's almost a moot point trying to find axles from a 4cyl. 

This is actually incorrect.  My 98 2dr SE XJ came from the factory with 4.0, AW4, 4x4 and 3.07.  It's really slow.  

 

The Liberty C8.25 would be the cheapest and easiest swap, followed by a C8.25 from and XJ with a Liberty disk brake swap.   You have lots of options tho. 

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19 hours ago, Minuit said:

I believe some early (very early) XJs could have 3.31s as well. I've heard some tow package XJs had 3.73s but never seen anything to back that up.

I have a D30 out of an early XJ with the V6 engine that has factory 3.73 gears.  It is a high pinion non-CAD axle.  Pulled it for future use when I convert the MJ to 4wd.  Sourced a factory MJ D44 for the rear with 3.07s.  Will be swapping in 3.73s and a Truetrac.

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Waaayyyy back when, when I knew squat about Jeeps but had my MJ, I bought a D30 out of an 86 XJ (actually helped pull it out at the guy's house) to start my 4WD conversion.  The guy (a long ago member from the Yahoo group days) flat out lied to me, saying it was a 4.10, which matched my rear D35).  When I got to install it a few months later, I made the sad discovery that it was a 3.73.  Stock axle out of an 86 XJ with a 2.8 and a TF904 tranny.

 

That was my rather rude awakening into the Jeep world, LOL.  I've never heard from him again.

 

Cool starry bra, I know.:laugh:

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The 84 through 86 years had a wide variety of axle ratios. I have an '86 XJ 4-cylinder 5-speed with 4.10s; the running gear from an '86 XJ 2.8L V6 auto with 3.73s; and I had (and gave away) an '84 XJ Wagoneer 4-cylinder auto that had either 4.56 or 4.88 gears in it.

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2 hours ago, mjeff87 said:

Waaayyyy back when, when I knew squat about Jeeps but had my MJ, I bought a D30 out of an 86 XJ (actually helped pull it out at the guy's house) to start my 4WD conversion.  The guy (a long ago member from the Yahoo group days) flat out lied to me, saying it was a 4.10, which matched my rear D35).  When I got to install it a few months later, I made the sad discovery that it was a 3.73.  Stock axle out of an 86 XJ with a 2.8 and a TF904 tranny.

 

That was my rather rude awakening into the Jeep world, LOL.  I've never heard from him again.

 

Cool starry bra, I know.:laugh:

 

Are you sure he lied, or was just bad at math or counting turns?

 

I've been there.  I bought a 14 bolt FF out of a square body Chevy for my XJ.  Buddy was like "Yeah, it's 4.10.  It should be at least.   I look at the tag on the front axle and I'm sure it is.  Then we spun the yoke and it went around 4 times."  And on and on.  It sounded flaky but I went with it, and didn't feel like crawling in the mud to look at the front axle.  Pop the cover when I get it home and it's 3.73. :laugh:  Wound up needing the carrier for the next axle I bought, which actually had 4.10s, plus I got one with the better style housing.

 

My YJ friend bought a YJ D30 off the guy I bought my MJs off of.  Same thing, was supposed to be 4.10, nope, 3.73.  Knowing the guy he bought it off of, he just didn't know any better.  If anything whoever that guy got it from told him it was 4.10s and lied (or also didn't know any better) and the axle was again resold with the same bad info. :laugh:

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Nope, he flat out screwed me.  I was a greenhorn and he knew it.  In retrospect, though, I'm really not that upset about it.  Judging from his place, he and his wife really needed the money (for rent, or heroin, or.......).  I just chalk it up to a life lesson.  He coulda told me it was a D70 full float with a Detroit in it and I woulda believed him at the time.  I knew nothing.  But that's when I started learning.

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