MJ gearing options

Well, I'm doing an emergency axle swap in my MJ this weekend. I happened to have an 8.25 from an XJ w/ 3.07's laying around. I am most certain it does not match the front in the MJ.

... anyone know what is the most likely ratio for an '86 MJ with a 2.5L and 5 speed? Just wondering what I'll need to match things up later ... it'll be a 2wd for now.

Thanks!

Most likely 4.10s with the *small* possibility of a 4.56 ratio. Is there a tag on either the front or back diff?
Jeep on!
--Pete

Pete M said:

Most likely 4.10s with the *small* possibility of a 4.56 ratio. Is there a tag on either the front or back diff?
Jeep on!
--Pete

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Pete,

Nope, no tags ... couldn't be that lucky. :banghead:

I thought 4.10's were likely ... I'll sure want to make sure it doesn't go into 4WD w/ a 3.07 rear and a 4.10 front axle! :doh:

I guess after it's back together and running I'll pull the cover off of the D-35 and count ... if there's any teeth left! I had the drivers side wheel and axle shaft pass me this morning, so something is screwed inside! :scared:

Should be 4.10's as mentioned. Ummm one thing though, I always thought the MJ was spring under axle and the XJ is spring over... maybe I'm wrong as I don't happen to have an MJ yet in my collection. This might complicate your quick swap quite a bit... unless you are going for the jack rabbit look, but I think the perches are at a different width as well, hopefully someone else here can confirm whether I'm right or wrong though... sorry.
Mike B.

Some MJ's came with 3.55's from the factory. Mine did. Don't know why though??

SewerBoss said:

Some MJ's came with 3.55's from the factory. Mine did. Don't know why though??

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4.10s camoe on 4cyl engines, 3.55s came on 6cyl engines

84-86 could be ANYTHING

3.07, 3.31, 3.55, 3.73, 4.10 or 4.56.

there's NO way to know without checking the numbers on the ring.

1986xj said:

Ummm one thing though, I always thought the MJ was spring under axle and the XJ is spring over... maybe I'm wrong as I don't happen to have an MJ yet in my collection. This might complicate your quick swap quite a bit... unless you are going for the jack rabbit look, but I think the perches are at a different width as well, hopefully someone else here can confirm whether I'm right or wrong though... sorry.
Mike B.

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You are correct, the perches need to be a little closer to the diff for an MJ...and it is spring under from the factory. XJ axles can be done in an MJ, but it takes a little work.

Phil Weeks said:

You are correct, the perches need to be a little closer to the diff for an MJ...and it is spring under from the factory. XJ axles can be done in an MJ, but it takes a little work.

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You are all correct, MJ's are spring under. This MJ was already converted to spring over, so dropping in the 8.25 from an XJ was just a bolt up process. As for the width on the perches from the diff, everything dropped in so it must be real close.

FYI, this MJ (Mutt Jeep) had 3.54 gearing (D-35 ring gear stamped 46-13, 3.54 ratio). Now it's really a mutt with a 3.07 geared 8.25 out back and a 3.54 geared D-30 up front. I can tell that 3.07's with the 2.5 and 5 speed has no power ... but it should get great gas mileage!

As for what caused this mess ... it looks like the bearing went on the axle and took out the axle retainer (non c-clip axle) allowing the drivers side shaft to leave. It mangled the shaft and end of tube for sure, was easier to swap since the 8.25 was sitting here.

Once I get a primary vehicle and bump the MJ back to project status, I'll have to consider what the gearing and axles will be in the future ... also what drive train will replace the tired 2.5/AX5/NP207 combo.

The 2.5L has the same patern as the 2.8, 3.1, and 3.4! So you could swap in the 3.1 or 3.4 but IMHO the 2.5 from 91-96 is the power plant that I did. The MPI 2.5 puts out about 140 HP which is comparable to the 160 or the 3.4!