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swapping to an MJ

strokedwoody

NAXJA Forum User
Location
greensboro,NC
After several years of wheeling the unibody on my 87xj has had it. Full of dents and battle wounds, I decided to get an MJ, less body and glass. My plans are to remove the bed, tube the rear and incorperate an exocage into it.Currently my xj has a full width 9" in the rear,44 front using all the factory mounting points. One of my concerns is rear springs,I currently have bigoffroad 8" leafs, from taking a quick look at the MJ I bought (I don't have it at my shop yet) it doesn't look like I will be able to reuse my rear springs. If that's the case I plan on 3 link in the rear and swayaways. This would also get me back to the 108 to 110" wheel base I was hoping to have. Another concern is are there any differences in the front end set up on an MJ? doesn't look like it to me,but figure I better be prepared if there is. Is the steering box mounted in the same way and will my current steering set up gong to work as well?(it should if the box is mounted in the same way it is on my xj).It may all be identical to an XJ, it looks like it is to me, with exception of the rear end.
I plan on using my current drive train also,(a fresh stroker motor with about 200 miles on it,auto, and 231)I'm sure I'll have to retube the rear driveshaft. the MJ is an 88, looks to me like I can use the same harness and connections and just pull my motor,trans, and t-case together, drop it in , plug it in and roll, am I missing anything?
I plan on pulling the drivetrain,bed and sending the cab to be painted(deep burgundy with large metal flakes,bass boat stlye) the building the exocage and rocker protection. Then building my rear suspension, if the leafs won't work. Finally taking a weekend or two for swapping in my axles and drivetrain from my XJ. If I'm overlooking something please advise me. I'm posting b/c I know someone has done this already, as I said my main concern is the rear suspension,I'd like to keep my leafs if possible to keep from dumping a lot of cash in it all at once. The beauty of this is I got the running MJ with 98k , 4.0, 4wd,auto with air ,for $300.I couldn't pass it up. Also the cage from my XJ and all the drivetrain parts from this MJ will be for sale. For those who have seen my XJ "BIGWOODY" the cage is very well built DOM wich I can cut out in about two or three pieces. Thanx in advance for the help.
 
As far as relocating the perches, thats not going to b e a problem. I had planned on doing that anyway to adjust the pinion angle for the added wheel base. I really am wondering about mounting the rear springs I already have, even if I need to move the spring hangers forwards or backwards to accommadate the springs. I haven't looked at the frame to see if this is going to be a problem by the frame curving down in front of the forward spring hangers.
 
MJ springs are Spring Under Axle, and are really great being about 57 inches long. Do a simple spring over to et you about 6 inches, and mix and match a leaf or 2 from another vehicle to get more. I have about 8 inches on my MJ with a spring over and I mixed some leaves in and out from a Waggy front pack. then sell you XJ springs and make some money. you could always 3 or 4 link the rear, it would be much easier with an MJ than XJ, but tons more work than keeping the leaves.

if you have a shortbed MJ it will be 113 inch wheelbase, if you want to leave the gas tank in the original location, you can slide the rear axle forward maybe 3 or 4 inches, which would be pretty easy to do moving the leaf spring mounts.

everything up front is the same as far as geometry, but the LCA frame mounts have an additional brace, and the crossmember has more attachment points.
 
mad maXJ said:
MJ springs are Spring Under Axle, and are really great being about 57 inches long. Do a simple spring over to et you about 6 inches, and mix and match a leaf or 2 from another vehicle to get more. I have about 8 inches on my MJ with a spring over and I mixed some leaves in and out from a Waggy front pack. then sell you XJ springs and make some money. you could always 3 or 4 link the rear, it would be much easier with an MJ than XJ, but tons more work than keeping the leaves.

if you have a shortbed MJ it will be 113 inch wheelbase, if you want to leave the gas tank in the original location, you can slide the rear axle forward maybe 3 or 4 inches, which would be pretty easy to do moving the leaf spring mounts.

everything up front is the same as far as geometry, but the LCA frame mounts have an additional brace, and the crossmember has more attachment points.
Right now I'm running 38.5's with about 10" of lift, I'm trying to cut more off the fenders of the MJ and with getting rid of the bed, hope to run the same tires with less lift. was hoping for around 7 to 8". another question.....will long arms for an xj work on an mj as well?
 
I'm pretty much in the middle of the same project. Swapping the drivetrain and running gear from my 90 XJ to my 89 2WD MJ. As has been noted, the frontend is exactly the same as on an XJ. Meaning you can use the same lift options. As far as the longarms, I'm not sure, I believe the MJ crossmember is a little different, it's raining out or I'd go take a look at it for ya. My XJ is about 8" running 35s. I hope to bring the MJ down to about 6" with the same 35s. I will be using the longarms I built for the XJ and in the rear I plan to go SOA, plus extended shackles, and maybe a little taller perche mounts. The longer MJ leafs should ride better and flex better. I plan to sell my XJ leafs for a few $$.
 
I'm currently running an MJ with a full width ford nine and the matching HP D44. I run the stock Mj leaves in the rear but spring over and 2" blocks. I know blocks suck but I have yet to have any problems with them. The Mj springs actually flex really nice. I'll soon be swapping in a D300. Here's a few pics, I have a ton more if ya want, if ya have any questions feel free to ask.


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mad maXJ said:
have you measured your actual lift height? SOA and 2" blocks should be 8 inches, but yours looks like more than that... maybe it's the high cut flares, but the position of your wheels relative to the body looks like more than 8"





When I did the flares I removed about 3-4" of sheetmetal and raised the flares accordingly. My tires stuff into the wheel wells pretty well now. I can get close up pics if you guys want. I also just removed the lower sheetmetal behind the rear of the flares and under the taillights. Judd :yap:
 
Hey Greg!

As noted the MJs have different spring pad width... (slightly narrower than XJs) they have longer leaves that mount under the frame, not outboard of it like XJ)

Also the rear 'frame' flares outward behind the crossmember. IIRC the x-member is the same as XJ though....its EVERYTHING behind it + the driveshaft that changes up.

Going bedless including a fuel cell? That allows the rear axe (with shorter XJ leafpack?)to come forward a lot more than keeping the OEM tank. I'd do some quick tape-pulling & see how high you'll sit and where the axle will center up (wheelbase) with the BORs then plan the next move.

I loved my SOA MJ setup though. Very good performance and CHEEP. One drawback was lots of rear overhang, but ya get that with any 'normal' leaf-sprung setup.

HTH and keep us posted!
 
This is a good post. I am very close to doing a similar project. Unfortunately all I have found around town are longbed MJ's. Anyone bob theirs? Did you take some out of the front to decrease the wheel base and some out of the back to decrease the overhang? Or did you take it all out of the back?
 
Well, after talking and getting ideas from the guys I regularly trail ride with, I decided to probably 4 link the rear, set the wheelbase at 108", and whack the rest of the frame off. We are going to cut the skin off the bed, narrow the rear with tubeing and narrow the tail gate, as well as cut the bottom out of the bed. Can't wait to get started,but I'm not taking mine apart until I have all my paint, cage ,and body work complete. thanx for all the input.
 
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