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  #1  
Old 07-26-2005, 08:38 AM
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I read somewhere the other day that MJ springs (SUA) are 57" long. Can anyone with an MJ confirm this?

We measured a Grand Wag yesterday also to be at 57" long SOA.

Unless my calculations are failing me, that would mean that a stock MJ rear spring pack would provide 4"-5" lift and would be a bolt on for the rear of a Wagoneer/Grand Wag (and possibly Cherokees too). (Assuming both of them have the spring pin in the center).

I'm willing to be the guinea pig, but wanted to see if anyone can confirm that the MJ springs are indeed 57" before I go trying to find some in a junkyard.
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Old 07-26-2005, 09:01 AM
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This thread shows that MJ springs are 57", but it looks like the pin is not centered on the main leaf.
http://www.naxja.org/forum/showthread.php?t=55515

I didn't look while measuring the other day, but IIRC, the FSJ rear springs are centered. Is that right?

I guess that means there would be a change to the length of the wheelbase if you went with MJ rears....

Something for all the folks with all the bobbed rear ends to think about. Swapping to MJ springs could save you an inch or two of rear overhang while providing some lift....

[ July 26, 2005, 03:03 PM: Message edited by: jode ]
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Old 07-26-2005, 09:05 AM
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One more thought (since I am enjoying this conversation with myself so much )
If you went to a D60 rear, the pinionn lenght is longer than a 44 right, so instead of modifying your D-shaft, you could just install MJ springs, and maybe the offset would be enough to compensate for the longer snout on the 60 so no d-shaft mods would be required.
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Old 07-26-2005, 10:14 AM
waggin'ear waggin'ear is offline
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Jode,

FSJ rear springs (76 and up and 74-76 131" wheelbase J-trucks) are 57" long and offset about 4-5 inches with the pin towards the front and 2.5" wide.

Don't know what the diff in spring rates is or if the eyes can accept the correct bushings.

Interesting idea.
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Old 07-26-2005, 10:20 AM
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I bleev the eye bushings won't be a problem because all the folks using those revolver shackles on FSJs just buy XJ revolvers and they are the same iirc.

This is getting interesting though...so the MJ leaves have an offset center pin, and the FSJ springs have an offset center pin. UNless someone else here chimes in to state that this is all BS, it looks like the next step is to grab some MJ springs and start test-fitting....
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  #6  
Old 07-26-2005, 12:39 PM
Richards Richards is offline
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Keep us updated
I'd really like to know if it works out. It would be nice to find cheap 4 inch lift springs for the rear
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Old 07-26-2005, 01:31 PM
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Bushings should be no big deal for 76-91, they just need to wind up at a 9/16" ID for the bolt, lots of options, as that is a common size.
This Comanche spring thing went around about 2 years ago, with me bugging people and no real #'s/pic's ever presented.
If it works that's great, but I could not wait, had to move on.

Joe, thanks for picking up the ball on this, I hope it pans out.
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  #8  
Old 07-26-2005, 03:34 PM
tkiller13 tkiller13 is offline
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Ill measure my xj springs tommorrow and check where the pin is. Not sure if they are the same. Mj pry have a bigger springrate. Xj are soa.

[ July 26, 2005, 09:37 PM: Message edited by: tkiller13 ]
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Old 07-26-2005, 04:34 PM
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These pics kinda sorta put a cramp in the whole theory. These are stock MJ springs except that there are two MJ main leaves to combat sag.







These pics seem to show that you wouldn't really seem to gain much in height over FSJ springs. Any thoughts?
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Old 07-26-2005, 05:07 PM
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They look jut as flat as ours heh. The XJ's were spring under until 93-94. But use shorter springs.
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  #11  
Old 07-27-2005, 03:20 AM
tkiller13 tkiller13 is offline
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Quote:
Originally posted by Stuka:
. The XJ's were spring under until 93-94. But use shorter springs.

This is my 86 xj spring over axle. I had a 93 that was the same. All xj's were the same.
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  #12  
Old 07-27-2005, 03:38 AM
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Yep, XJs are SOA factory in the rear like FSJs.

Quote:
Originally posted by Stuka:
They look just as flat as ours heh.
Yeah doesn't look like much of an improvement....
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  #13  
Old 07-27-2005, 05:22 AM
Richards Richards is offline
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What vehicle are those pics of? How does the weight of that vehicle compare to an FSJ?
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  #14  
Old 07-27-2005, 05:37 AM
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The ones I posted pics of are on this:


[ July 27, 2005, 11:39 AM: Message edited by: jode ]
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  #15  
Old 07-27-2005, 12:26 PM
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Hmm, ok. For some reason I thought older XJ's were spring under. Learn something new every day I guess [img]smile.gif[/img]
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  #16  
Old 07-27-2005, 11:13 PM
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Quote:
Originally posted by jode:
One more thought (since I am enjoying this conversation with myself so much
lol,id have jumped in but i just got back

anyway,i was going to speculate that MJ springs were too soft to give any real lift.if they were stiff enuff to carry any real load in an mj,and support the weight of a FSJ while maintaining the arch,then an unloaded MJ would ride very stiff.

from the pics,it kind looks like the too soft theory has some supporting evidence
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  #17  
Old 07-28-2005, 03:05 AM
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Yep, well, I figured that the rear of a Wag might need some lightening (chop/bob) and the MJ springs would need some adjusting (add a leaf or two), but it is looking like they would contribute very little lift even if FSJs weighed exactly the same as MJs.
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  #18  
Old 07-28-2005, 08:05 PM
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i had an 90 xj and used dodge rear springs for lift. i think it was early 80-88 kota springs. cut the main eye off and used my stock main leaf. not sure on the measurments though id have to check. just throwing that out there.
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Old 07-29-2005, 03:04 AM
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Let us know how much it lifted it.
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  #20  
Old 07-29-2005, 05:55 AM
Matty Matty is offline
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aren't XJ and MJ springs the same measurements?
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