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MJ spring length?

I

IdahoEagle

NAXJA Forum User
Location
Boise Idaho
Will MJ springs work on an XJ? I know they have a much higher arch, but is the mounted length the same? I'm looking at these for the back of my Eagle wagon when I straight axle it next weekend. The stock Eagle rear springs are the same exact length as the XJ rears, just with smaller bushings and different type of shackle. All help would be appreciated.
 
MJ springs are about 5" longer than XJ springs. Not a good candidate unless you plan to relocate the mounts.
 
Dakota or S-10 leafs replacing the stock leaves -- leave your stock main leaf in place. Do a search and you'll turn up the recommended years for the Dakota packs -- the newer ones are spring over and won't work.
 
Hey Eagle I got what is probably dumass Question but Ive been wondering about this since I picked up a set of leafs for a comanche along with some xj parts at a swap meet. If I put the mj springs on my xj wouldnt I get a bunch of lift? Would it work or would have a bunch of problems like geometry, spring wrap, drive shaft length, ds angle, ect. Like i said before its probably a dumass ?
 
You can take the Comanche springs apart and use everything except the main leaf to replace all the seconday leaves in the XJ packs. That should lift you maybe 3 or 4, maybe even 5 inches. I didn't understand that you already have a set of MJ springs -- I thought you were getting ready to go shopping.

'Course, being an MJ lover I hate to see a good pair of MJ springs be taken apart, but ... ya gotta do what ya gotta do.
 
So where is the length differences in the MJ springs? Yes I already have a set, came from an 86 that I'm parting out for axles for the Eagle. Another question for you, how good does the AMC20 rear end in the MJs hold up? I'm planning on using 32" or 33" tires with moderate trail use with a lot of pavement use. Also, I am parting the rest of the truck out, no bed, already gone, but I have the cab, nose, and I have a title.
 
I think the springs are 3" longer in the front and 2" at the back... i think. That AMC 20 will hold up pretty well, it doesn't have the infamous 2 piece axles like the CJ AMC20s, it's roughly D44 strength. Regardless, I would be a decent choice for 32-33s, but I believe it only can be geared as low as 4.56, so if you're ever thinking of going bigger than 33s I would look for something else.
 
The shafts look like the fullsize version, with welds on the ends, not nuts. I guess I'm just going to have to break out a tape measure when I get to the shop tomorrow to find out about the length for myself. I really didn't want to crawl underneath it yet, but oh well.
 
I believe BrettM is correct -- 5" longer overall, split into 3" forward of the axle and 2" aft. If that's not correct, then it's the opposite -- 2" forward and 3" aft. It isn't all forward or all aft.
 
Ummm....sorry to resurrect an old post, but does anyone actually know (or would someone be so kind as to measure) the actual eye to eye length of a set of MJ springs?

TIA ;)
 
~57 inches when they are flattened out (which mine are all the time now-a-days) and with about 31" behind the pin.
Jeep on!
--Pete

ComancheClub.com
 
Thanks,
So, with a smidge of work on my handy dandy calculator, that means that it is 26" from the front eye to the pin and 31" to the rear eye. So the center pin is 2.5" offset right?
 
I hust mearured a set of (uninstalled) Metric Ton leafs:
53.25" center to center. The leaf center bolt was apprx 24.75" from the center of the front bushing
 
Sure, plus or minus 1/4". What do you need that measurement for?
Jeep on!
--Pete
 
:gag:

Actually, I am trying to figure out how to get them on my FSJ
The eye to eye is the same, but I bleev FSJ ones have a centered pin, so it is getting tricky....

Thanks for the info though :us:


EDIT - just found out that FSJs are offset too, so this may be a bolt-in swap type situation.
 
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Unless the leafs came from a Metric Tonne MJ, I doubt they'd be strong enough to hold up a FSJ. The MJ is a pretty light-weight vehicle. I had to double up the main leaf in mine to counteract the rollbar/bumper/etc and even then they are just about flat.
Jeep on!
--Pete
 
Thanks for the info.

Working with some modifications here.
1. On the FSJ, the stock configuration is SOA, so a smidge of sag is no worries - the MJ leafs will be adding a bunch of lift (like if they were installed on an XJ iirc)
2. Once the top is off and the rear end is bobbed, there won't be any more weight back there than on an MJ ;)

One more question - you mention the metric tonne MJ...what are the other types of MJs? One other consideration is that once you get it all set up, you can alway add a few more leafs to the pack to adjust the spring rate right?
 
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I still recommend the doubled leaf to help control springwrap, unless you're doing something else to control it. I've had good success with it with absolutely no loss of articulation. The MJ leafs are long and thin and flex like mad. I personally think they're the best ones out there. :D Oh, and 4wd leafpacks have about 1 inch more height than 2wd packs. That's "from the factory" though, and the years have been harsher to some trucks.
Jeep on!
--Pete
103748808.jpg
 
Righteous rig, and thanks for the info. Doubling up the main leaf sounds like a great idea if it maintains flexibility. Now i just have to find two MJs that are looking to donate :D and see if this will work.

BTW, if you have pics of your springs while they are installed on your rig on a flat surface, I would be interested in seeing them...maybe a view from the rear spring eye towards the front spring eye from about the same plane as the springs praps?
 
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