XJ to MJ parts interchange

I have a nicely modded XJ. It came stock with a D44 rear axle. I put in a full detroit locker and regeared to 4.88's. Front axle is non disco D30 with an OX locker and 4.88's. For lift I did a Rubicon 4.5inch with Clayton long arms and upgraded track bar etc...

Now I just picked up a 1990 MJ metric ton edition. It has a D44 rear axle. I am trying to develop a strategy for moving the good bits off my XJ onto the MJ.

My preliminary searches are giving me pause. It is not clear that I can re-use the rear leafs from the XJ and it seems that the rear axles might be different... spring over versus spring under.

Any advice would be appreciated.

Thanks,
Matt

The MJ springs are longer so you cannot use the XJ leafs. And it's typical do due a spring over on the MJ to get a lift on the rear of 4.5" or greater. Most your goodies however from the XJ should and will fit on the MJ. Check this site out as well...http://www.comancheclub.com/forums/index.php

agreed with minibeast

basically anything from the front seats forward is interchangeable. except, the only doors that are interchangeable are the 4 door front doors onto a comanche. 2 door doors are 9" longer.

from there back, you're all MJ

The MJ and XJ 44 axles are the same width, however the spring perches are under-and spaced closer to the center- on the MJ. The XJ has the spring perches on top and wider apart. (The XJ leafs attach outside the 'frame' where the MJ mount underneath it)

Also the XJ 44 has lower shock mounts attached LS rear, RS front... The MJ has the shock mounts on the leaf clamps, and both face forward.

Pretty much everything from the trans crossmember forward interchanges between an XJ & a MJ.

MJ doors = 4 door XJ front doors. The MJ LCA frame mounts are 'boxed'

woody said:

Also the XJ 44 has lower shock mounts attached LS rear, RS front... The MJ has the shock mounts on the leaf clamps, and both face forward.

Click to expand...

correct on the xj shocks being different. however, the location (front or rear) of the shock mounts for the comanche varies depending on short wheel base or long wheel base (shortbed vs. longbed) applications.

shocks are located both behind the axle on the shortbed, and both in front of it on the longbed IIRC. i was just under my longbed comanche swapping out the axle the other day and for some reason can't recall....pretty sure i got the sides correct

OK so if my reading is correct...

To move my goods to the MJ I would need to modify the XJ axle or move the internals over to the MJ. Beyond that the MJ rear springs will need to be replaced; I can't imagine the heavy duty spring pack it has flexing so well if I just did SOA.

So the end result would be a long wheel based rig, with a poor break over angle, and too much rear over hang. With costs being new rear springs and rebuilding an axle.

The MJ would excel if I was wanting to go for more lift, fit larger than my 33" tires, shorten the wheelbase a little, and bob the rear of the bed / put a flat bed on it.

I think the closest I can get to having my cake and eating it too is to keep the XJ as pure toy and use the MJ as a four wheel drive pickup. I was hoping to eliminate a vehicle and make one serve both functions. I need to take the garbage cans to the end of the road and haul landscaping materials around my lower property; but want a rig as capable as my XJ for playing.

The hope was to combine the two, for little to no cost, but I am having my doubts.

why don't you head over to comancheclub.com and we can point you to ways to make it cheap.

most likely you don't have a "heavy duty" spring pack. the metric tonne springs still flex just fine. especially when loaded with trail spares and such.

it should be a longbed correct? if it's a shortbed, departure angle isn't exactly terrible, and bobbing the bed isn't all that hard.

frankly, i think with your concerns, should DD the MJ for now, while doing a project on the xj...half cab the xj with an mj rear portion, and cage it. then you will have a truck and you can still use more commonly available parts.

why do you want to switch the xj's rear axle into the mj? and, it costs about $25 for spring perches and maybe $70 to have the perches welded on. i suggest tac-welding the perches while under the truck with the pinion angle set correctly.
if you're concerned about welding, get to your local chapter of naxja, find someone nearby with a welder, and offer a few beers. i'm sure another good jeeper will be willing to help (cause it isn't exactly a hard project)