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1991 MJ build thoughts: 2wd->4wd, lift?

kastein

NAXJA Member
NAXJA Member
So I've finally convinced a friend of mine to buy an MJ off craigslist, with help from a mutual friend with a lifted ZJ. Assuming it isn't too rusted out to be worth it - specs:
* 1991 Comanche Eliminator
* RWD, AW4 tranny, 4.0L Renix (unless 1991 was HO? I forget.), SUA rear axle, unknown if rear axle is a d35 or c8.25

What I'm thinking we should do to it:
* first thing: transmission lines need replacing. No big deal, a hundred bucks at NAPA or 65 at RockAuto if it'll last long enough for them to be shipped.
* convert to SOA using my old rear c8.25 at the end of the month after the all-you-can-carry at Hollands Junkyard. I think this will net around 3" of lift probably?
* convert to 4wd and lift the front at the same time, using my old d30. I have a spare 21 spline aw4 that was given to me, if I'm correct, this should mate perfectly with a 1991 transfer case from a junkyard. Am I wrong? Is 1991 23 spline? I'm constantly forgetting whether the switchover was 90-91 or 91-92 on that.

What I think we'll need to do this:
* new aw4 (I might have one) with the different tailhousing, or swap parts over. New aw4 is easier.
* a 231, obviously - should match the aw4 spline count and have the pre-96 tailhousing for the slip yoke.
* a d30
* a normal front driveshaft from an auto XJ - is this the right length? I'm pretty sure it is, since MJs are the same from the seats forward and a 4.0/aw4/231 is going to be the same length in XJ/MJ.
* a new rear driveshaft for an auto 4wd MJ, possibly lengthened - I can get one out of a manual 4wd MJ with a d35 SOA, I'm worried this may not be long enough since it's manual instead of auto, but it might be longer due to the d35 pinion being shorter? I really don't know.
* front coil lift installed at the same time as the new front axle to match S, not sure what yet.
* maybe a new transmission crossmember. Not sure. Will a stock aw4 4wd XJ crossmember fit?

Thoughts, please... ESPECIALLY on the rear driveshaft length, tranny spline count, and crossmember. Those are what I'm most worried about.

EDIT: all brake lines will be replaced immediately. New bolts will be procured for every part of this install, I hate dealing with rusty bolts and worrying that they're going to break off and leave me SOL.
 
you cant just drop in an xj 8.25 without modifing the spring perchess, the spring-width (dont know the proper term) are differant.
mj's have the leafs mounted under the unirail, xj's are outboarded. you will need to re-weld the perches on.
its CLOSE, but it'll wear out leaf spring bushings like mad if you try.

soa will net you about 5" out back. im not too sure about the 4x4 comanche's, but you might want to budget for a SYE just in case. all my experience is w/ 2wd shortbed's.
 
OK, cool, thanks for the heads up on that... guess my welder is gonna get more of a workout than I planned. It's a 2wd with a long bed (I think, 6 foot is the long bed version right?)
 
long bed is 7ft. SOA usually nets around 5-6". 91 is the HO engine. your best bet would be to find a AW4/231 out of a similar year MJ/XJ.
 
I have a long bed MJ with an 8.25 and SOA. I got just a bit over 5" with the lift. You will not need an SYE, but you will need longer shocks and extended brake lines.

Don't forget that when you lift the front to match the rear, you will need lots of stuff .... adjustable upper and lower control arms, adjustable track bar, longer shocks, longer brake lines, and I would highly suggest control arm drop brackets!
 
I'll have to remember that, thanks... I was considering suggesting a longarm setup if he decides to lift it, after I realized how high it'd end up. I was only expecting 2-3" out of converting SUA to SOA!

Good to know about the SYE not being needed, and the brake lines and such being needed - is this because of the longer driveshaft and therefore less severe angles, or something else? At this point I'm expecting to be rewelding the spring perches on the rear axle anyways, so I can probably help him dial in the pinion angles pretty close to ideal without resorting to shims. How much is your slip yoke engaged with the SUA to SOA conversion? Did you have to switch driveshafts or get it lengthened at all?
 
If you only want to lift 2-3", you don't want to go SOA......2WD leafapacks are about 1" shorter than 4WD ones too. You could swap a set of 4WD packs in the rear with a set of chevy drop shackles and probably get close to what you want. Or buy a set of lift packs (Hellcreek comes to mind.....)

a good resource ----> www.comancheclub.com

:cheers:

Jeff
 
If it is an Eliminator, it will be a short bed, bucket seats, full center console. Whats the asking price? I'd be all over this '92 myself. Oh, and '91 was the first year for the H.O.

http://providence.craigslist.org/cto/1372690472.html

So would I, but that's out of his price range and I don't have the budget for a project vehicle (other than my DD :D) right now, as I'm partway through buying a house. He's picking up one for six hundred bucks unless someone else buys it first. I love it because it means I have two jeeps to work on instead of one, and one of them doesn't even hurt my wallet...

EDIT: TekkaMaki, yes - it is. Looking at it tomorrow evening unless someone else buys it first; his Honda is on its last legs so he's been looking for a vehicle and I suggested it.

EDIT2: I tried to harass him into buying one from xjbump for a decent price, sadly it's out of his price range and even peer pressure from our friend with the ZJ didn't work.
 
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I looked at it last week....I wouldn't want to discourage you from looking at it because it is a low price but be prepared, it's pretty crusty underneath and has a ton of gobbed on bondo.

you've got a pm :sunshine:
 
UPDATE: MJ has been purchased.

The good:
* it shifts like a dream, even though the transmission fluid is filthy enough to be mistaken for old-engine used motor oil with ten thousand miles on it. Anyone have a good 23 spline AW4 with a 4wd tailhousing they for some reason want to trade for a 23 spline AW4 with a 2wd tailhousing?
* nice aluminum wheels, tires are in decent shape
* seats are in GREAT shape, so is most of the rest of the interior
* floors appear mostly solid, at least compared to mine. This isn't saying much though.

The bad:
* all transmission lines need to be replaced, as expected: $65 or so on rockauto.
* factory fogs rusted off long ago. Front/rear bumpers look good though.
* all brake lines look fairly rusty. Need to check them over, probably will replace for peace of mind.
* front straight tube axle housing is extremely rusty, so are the shock mounts and spring perches (can see through the rust holes in the sides of them :scared:.) Will disappear in the 2wd->4wd conversion anyways
* frame needs to be reinforced in some spots where it's rusting really badly.
* rear is a d35. This will probably change to an 8.25 when I have my old one collecting dust on my porch after I (hopefully) upgrade to one with 4.10:1 gears.
* shocks are all rusted well past worthless, as expected
* the fuel pump ballast resistor is so badly cracked and corroded that it split in half when I poked it. It still runs though! I was shocked. I'm thinking we're going to simply shunt this out, especially since it's an MJ and the pump appears to be back under the truck bed.
* it has a headlight delay module. Not sure if this goes under good or bad really.
* the front coil springs are sagged so badly it looks like my XJ did when I had installed my rear 2-3" lift but still had stock front springs. Easy to fix, I have a spare set of decent stock coils leftover from my lift, will install them along with the d30.
* the fuel filter and/or lines are leaking pretty badly.
* the power steering pump sounded pretty angry, not sure if it just hadn't warmed up in a while or not.

The ugly:
* it's a definite "20 foot paint job" right now. Maybe even 30 or 40 foot...
* headliner is falling down like a tent, I got a spare out of the junkyard that's in somewhat better shape: $15
* rockers need to be redone - thinking rock rails anyways.
* the sides of the bed along the rear quarters and wheel wells are horribly bondo-patched and appear to be painted with house paint. So are the tops of the bed sides.
* the roof has a bunch of dents in it, including a fairly large one from a tree branch landing on it.
* the hood is dented and scratched to hell (thinking a junkyard swap will help this easily.)


TekkaMaki - sorry we didn't drop by, it was 7:30 or so by the time we got the transmission line patched and the MJ roadworthy enough to drive it home.
 
TekkaMaki - will have to do, have been looking for a while but haven't really read too much, just wandered around.

89eliminator - yeah, the best part? I get to work on it, but I don't have to pay for it. :roll:
 
Partway through patching the frame rail rust on the passenger side now. Managed to cut the affected area out (the bottom of the rail was toast, but the sides are nearly spotless! such luck!) and weld in the first section of 1/8" plate Sunday night. I'll be grinding the welds down smooth and adding 1/8" x 1.5" angle along each edge either tonight or tomorrow night. The affected section was almost exactly two feet long, right around the lift locating hole. Whose idea was it to spot-weld two L-shaped pieces of sheetmetal together, again? And why did they forget about corrosion and capillary action?!

EDIT: also, oil has been changed and the transmission lines arrive on the 22nd!
 
Well, the brake lines blew up just like I expected them to :)roflmao: luckily he was only doing about 5mph on a back road half a mile from the garage) so those have taken priority over everything else. Almost finished welding up the angle + plate on the passenger frame rail, the driver side should go much faster now that I know more what I'm doing.

Next: brake lines, transmission lines, hopefully will be swapping the front axle(but not the tranny/TC install so no 4WD for now) in two weeks or so, assuming I get my new axles this weekend and have them installed by the middle of the next week.

EDIT: sorry for no pictures - camera got stolen about two weeks ago, has not been recovered (as expected.)
 
Thanks... yeah I was worried about that. As soon as we get it fixed up it's his daily driver though, he totaled the Honda Sunday night driving back from NY. So the 4wd conversion will probably be greatly delayed.
 
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