Rear ends....Comanche rear ends that is.

[coolwind57]

Newby story here, so you guys that know this stuff like the back of your hand:  bear with me.  I'm at the grade-school level of MJs.  I thought this experience might interest those not so familiar with MJ/XJ rear ends.

 

So I was at the junkyard yesterday and ran into a fella that was pulling an axle from an XJ.  Being the proud new owner of an MJ...and desperately seeking knowledge, I was asking him about XJ/MJ rear ends.  This guy is a serious off-roader.  He had cooked two rear ends in like that last year.  I told him that I had the D35 and he confirmed what I had already read, that it is a basic, road-happy, medium-duty choice.  I told him that my truck was serving as transportation to work, light/medium hauling here and there and occasional drive-in-the-woods to pick up a load of firewood duties.  He said I'd likely be just fine.  

 

He loves the D44s he said, but his choice for his XJs were 8.25s.  His opinion was that the D44 is awesome and slightly better, but the 8.25s were plentiful and as hard as his is on rear ends, he rates availability higher on his priority list than slightly better strength and durability.    

 

One interesting experience he shared was when he cooked his last one.  Said he just came off the trail and was at a traffic light in town.  Nothing appeared out of the ordinary, no noises, nothing.  The light turned green and he found that he just couldn't move.  Said he dropped her in 4wd and drove her home that way.  Now there's a tip that this newby will remember.  BTW, I will be on the constant lookout for a D44 from an MJ.  I'll take it easy on my D35, and If I ever cook it, then I only want to do a swap one, final time. 

 

 

 

[Dzimm]

27 minutes ago, coolwind57 said:

Newby story here, so you guys that know this stuff like the back of your hand:  bear with me.  I'm at the grade-school level of MJs.  I thought this experience might interest those not so familiar with MJ/XJ rear ends.

 

So I was at the junkyard yesterday and ran into a fella that was pulling an axle from an XJ.  Being the proud new owner of an MJ...and desperately seeking knowledge, I was asking him about XJ/MJ rear ends.  This guy is a serious off-roader.  He had cooked two rear ends in like that last year.  I told him that I had the D35 and he confirmed what I had already read, that it is a basic, road-happy, medium-duty choice.  I told him that my truck was serving as transportation to work, light/medium hauling here and there and occasional drive-in-the-woods to pick up a load of firewood duties.  He said I'd likely be just fine.  

 

He loves the D44s he said, but his choice for his XJs were 8.25s.  His opinion was that the D44 is awesome and slightly better, but the 8.25s were plentiful and as hard as his is on rear ends, he rates availability higher on his priority list than slightly better strength and durability.    

 

One interesting experience he shared was when he cooked his last one.  Said he just came off the trail and was at a traffic light in town.  Nothing appeared out of the ordinary, no noises, nothing.  The light turned green and he found that he just couldn't move.  Said he dropped her in 4wd and drove her home that way.  Now there's a tip that this newby will remember.  BTW, I will be on the constant lookout for a D44 from an MJ.  I'll take it easy on my D35, and If I ever cook it, then I only want to do a swap one, final time. 

 

 

 

One thing you want to be weary of, and I'm surprised that guy didn't think of.  If your gears blow up and you go driving in fwd, the rear end could lock up at speed.  This is not only a huge safety issue but it could also snap a u-joint or twist the driveshaft since those still spin.  I would never recommend driving on a blown up axle unless you take the diff cover off and take the chunks of metal out.  Even then it isn't a good idea to drive it.  The exception to this is to drive it off the trail. 

 

Good luck on your search for a D44.  They are hard to find but you may be lucky.  If not, I'd recommend the C8.25.  You just have to cut the XJ bracketry off and weld on new spring perches.  Like he said, those are plentiful.  

[PCO6]

6 minutes ago, Dzimm said:

One thing you want to be weary of, and I'm surprised that guy didn't think of.  If your gears blow up and you go driving in fwd, the rear end could lock up at speed.  This is not only a huge safety issue but it could also snap a u-joint or twist the driveshaft since those still spin.  I would never recommend driving on a blown up axle unless you take the diff cover off and take the chunks of metal out.  Even then it isn't a good idea to drive it.  The exception to this is to drive it off the trail. 

 

Good luck on your search for a D44.  They are hard to find but you may be lucky.  If not, I'd recommend the C8.25.  You just have to cut the XJ bracketry off and weld on new spring perches.  Like he said, those are plentiful.  

I'm going to put a C8.25 rear end in my MJ as part of a 2WD to 4WD conversion.   I have the rear end and am just looking for a Dana 30 front end with matching gears.   I'll be welding on new spring perches as you pointed.   Will the stock MJ shock absorber brackets fit the C8.25 which has a larger axle tube diameter?   I haven't disassembled my MJ axle yet so I don't know if the shock brackets will accept a larger u-bolt.

 

Any info would be appreciated.   Thanks.

[coolwind57]

26 minutes ago, Dzimm said:

One thing you want to be weary of, and I'm surprised that guy didn't think of.  If your gears blow up and you go driving in fwd, the rear end could lock up at speed.  This is not only a huge safety issue but it could also snap a u-joint or twist the driveshaft since those still spin.  I would never recommend driving on a blown up axle unless you take the diff cover off and take the chunks of metal out.  Even then it isn't a good idea to drive it.  The exception to this is to drive it off the trail. 

 

Good luck on your search for a D44.  They are hard to find but you may be lucky.  If not, I'd recommend the C8.25.  You just have to cut the XJ bracketry off and weld on new spring perches.  Like he said, those are plentiful.  

oooh, good point.  Perhaps he "limped it" back home or something.  If I got the story correct, then I suppose he lucked out getting that thing home safely. 

[Jeep Driver]

There is nothing wrong with the 8.25 in an MJ, I have one, it's a good affordable choice. 

 

[HOrnbrod]

Even though I have a D44, tops on the coolness factor for me because of it's rarity has always been the AMC-20 rear axle. Only a very few of the 86 MJ models got them. It's a tough axle too.

 

[Pete M]

yeah, I regret not being able to keep mine when I sold my 86.  :(  plus I guess I don't really need a collection of axles.  lol.

 

my new favorite rear axle suggestion is the Liberty 8.25 as my '06  is a couple inches wider than an MJ stock axle (to better match the wide MJ bed) and can be had with factory disks.  plus KJs are super plentiful in the junkyards. 

[schardein]

42 minutes ago, HOrnbrod said:

Even though I have a D44, tops on the coolness factor for me because of it's rarity has always been the AMC-20 rear axle. Only a very few of the 86 MJ models got them. It's a tough axle too.

 

 

Before I owned an MJ, I ran across an 86 in the pic-n-pull.  It had the AMC20 axle (I know my axles), and really had me scratching my head, thinking it was a swap, but seeing it had the proper 5 on 5 1/4" bolt pattern.  It also had metric ton springs, which could have been new, as they had no rust on them.  I went home, did some research, and went back two weeks later.  They'd crushed it.  I still get mad when I think about it.  It had the tailgate, and makes me wonder if it had the metric ton emblem.  Like I said, I was new to MJs and didn't notice.

[carnuck]

Metric Tonne models '86 and '87 had Model 20 optioned rear diff. The axles are the toughest to find as all the ones I have found so far had the passenger's side one piece shaft missing. 

   When I sold my previous rig I had found a Dana 44 rear with correct everything but spring pads that went with it. 3.73 ratio and power lock from a 2wd '67 IH Travelall that came with same bolt pattern and center hole as MJs, but 2 piece shafts. 

 

I put an C8.25 in my last Eagle wagon and with proper blue tip saw trimming, I was going to use the stock shock mounts reversed but of course it took Dana 44 front springplates from a full size truck to bolt it in. 

 

The XJ D35 I put in my Comanche SOA in the rear got the same D44 cast iron spring plates (rotated sideways for the smaller U bolt pattern) 

   I still have '73 Jtruck after market front anti-swaybar plates to put between the spring pack and axle on my new Comanche to mount the shocks onto and run stock shocks in the rear. 

[HOrnbrod]

Wrong. No domestic 87 MJ models were equipped from the factory with AMC 20 rear axles. Possibly some export models got the leftover AMC20 axles but it's not listed as an option in the parts manuals. For 87 the only upgrade axle option for the XJ/MJ models was the D44 in various flavors. 

 

 

[88whitemanche]

On 9/3/2017 at 11:43 AM, HOrnbrod said:

Even though I have a D44, tops on the coolness factor for me because of it's rarity has always been the AMC-20 rear axle. Only a very few of the 86 MJ models got them. It's a tough axle too.

 

Yep love mine lol 

 

 

[PCO6]

For those who have put a 8.25 rear axle into their Comanche (I plan to) did you use the original lower shock brackets?   The original axle tube OD is 2.5" while the OD of an 8.25 axle is 3".  

[Pete M]

I elongated the ubolt holes when I installed my 9".  

[Jeep Driver]

I got my last set of3"x 9/16" ubolts from a tractor trailer supply/service shop.......IIRC, $4 each with washers and deep nuts.....about $21. 

 

 

I used a HD 5/8 spring plate and made my own shock mounts.

[carnuck]

On 9/3/2017 at 11:58 AM, HOrnbrod said:

Wrong. No domestic 87 MJ models were equipped from the factory with AMC 20 rear axles. Possibly some export models got the leftover AMC20 axles but it's not listed as an option in the parts manuals. For 87 the only upgrade axle option for the XJ/MJ models was the D44 in various flavors. 

 

 

 

Model 20 was available in the full size Jeeps even after the Chrysler takeover until they ran out of stock and a few '87 Export YJs had them.

 

I will look for the parts info before going further. 

 

Model 20 was also used front and rear in the early H1 Humvees. 

[Dzimm]

2 hours ago, PCO6 said:

For those who have put a 8.25 rear axle into their Comanche (I plan to) did you use the original lower shock brackets?   The original axle tube OD is 2.5" while the OD of an 8.25 axle is 3".  

Cut the XJ shock mounts and spring perches off the 8.25.   Weld on the new spring perches in the correct location for the MJ, then just use the MJ shock plates on the bottom of the axle.  The larger ubolts may have to be squeezed slightly into the holes in the plate but they will fit in the holes.

[HOrnbrod]

43 minutes ago, carnuck said:

 

Model 20 was available in the full size Jeeps even after the Chrysler takeover until they ran out of stock and a few '87 Export YJs had them. I saw one Shortbox MJ with the M20 with level sensor in Alberta. Since all '86s are longbox then it would have to be an '87. 

 

This thread is about MJs, not full size Jeeps or YJs. And seeing one 20 transplanted into a SWB MJ really proves nothing.

 

" Metric Tonne models '86 and '87 had Model 20 optioned rear diff" Do not start putting out bum dope again like the above or your posts will be deleted.

[PCO6]

1 hour ago, Pete M said:

I elongated the ubolt holes when I installed my 9".  

Not sure how to do multiple quotes but thanks to Pete, Jeep Driver & Dzimm.   That all makes sense.   I'll cut, grind, weld, etc. Just wanted to make sure the original shock mounts with larger u-bolts would work with a bit of modification.   Thanks!

[Eagle]

1 hour ago, carnuck said:

 

Model 20 was available in the full size Jeeps even after the Chrysler takeover until they ran out of stock and a few '87 Export YJs had them.

 

I will look for the parts info before going further. 

 

Model 20 was also used front and rear in the early H1 Humvees. 

 

Okay ... but the optional heavy-duty rear axle in 1987 XJs and MJs was the Dana 44.

[carnuck]

11 hours ago, Eagle said:

 

Okay ... but the optional heavy-duty rear axle in 1987 XJs and MJs was the Dana 44.

 

Have you seen any XJs with Model 20? 

[HOrnbrod]

Carnuck, why are you using a four year old "For Sale" ad in your signature? Is this vehicle still for sale? If so, move it to the Classified forum where it belongs.

[carnuck]

3 hours ago, HOrnbrod said:

Carnuck, why are you using a four year old "For Sale" ad in your signature? Is this vehicle still for sale? If so, move it to the Classified forum where it belongs.

 

I can't access the right page to delete with my iphone. Only part I can't get to for some reason. 

[Skorpyo]

13 minutes ago, carnuck said:

 

I can't access the right page to delete with my iphone. Only part I can't get to for some reason. 

Try this link: https://comancheclub.com/settings/signature/

[carnuck]

33 minutes ago, Skorpyo said:

Try this link: https://comancheclub.com/settings/signature/

 

That was it! Wonder why the link  wasn't visible with my phone?

[Sir Sam]

Like Pete said the 8.25 with disks is readily available at junkyards out of 2003+ Liberty's. I have one from an 05 diesel Liberty I'm using in mine, this has 3.73s and limited slip rear end. 

 

Some KJ rears even had 4.10s from the factory, if you find a renegade it may have the 4.10s in it. Most KJ rears will have 3.55s which is good for matching MJ fronts.