Mj Vs. Xj Leaf Springs And Skyjacker Add-A-Leaf Kits?

[GHayduke]

Hi guys,  I'm doing a 88-98 conversion and want to add 2" of lift to the rear.  I used spacers in the front for about 1&1/2 to 1&3/4 of lift.

I'm thinking of using a long add-a-leaf in the rear to give me around two inches lift.  I can then fine tune the hight with spring shackles if needed going forward. 

 

I'm using the factory 2wd rear springs (shortbed) and a 98' Chrysler 8.25 Axle in the rear.  I'm thinking of trying the Skyjacker 2inch add-a-leafs in the rear:    http://www.quadratec.com/products/76101_800_07.htm

I've had positive results with skyjacker springs on my CJs.

 

My concern is the specs for these show them as useable for both the XJ and MJ?  I thought the rear leaf springs were different as I had considered using a XJ leaf to beef up my MJ pack and was told that would actualy lower the rear. 

 

Does anyone know the difference between the leaf packs on the Cherokee vs the Comanche? 

 

Again I'm taking the rear apart to put in the newer axle and would like to start with spring leafs, leaving me the shackles for future lift adjustment.  What do you think?  Any info would be appreaciated... anyone tried these?   :dunno: 

 

I know I've heard they can fatigue and you loose the lift over time, but if so I could still do shackles....  

 

This jeep will be my daily driver street rig and not a trail rig.  I just want a little lift as MJs look low.

[onlyinajeep726]

The MJ leaf springs are longer eye to eye than XJ's.  Have you considered making a bastard pack using leaves from an S-10 or Dakota?

[GHayduke]

I saw Pete M said:  "  in the rear you can go with an 3" AAL (which, due to differences between MJs and XJs that the aftermarket doesn't seem to understand, generally lift around 2" in an MJ). "  in a past thread....

 

I then found:  Pro Comp Rear Helper Spring - Add-a-leaf's that are advertised as 3".. but in the description they say " Provides 1.5 to 2.5 inches of lift "

 

I'm concerned about ride quality with theses?  This is a cheaper spring that may be a rougher ride....?

 

onlyinajeep726: I've only heard of folks making bastard packs on XJ's... but would wonder how much lift I might get and at what ride quality???  Who's tried this?  Anyone here?

 

Does anyone know if there is a different curve / profile to the XJ vs MJ springs that comes into play?

 

[ComancheKid45]

I threw a 3" Hell Creek XJ AAL in my MJ and got right about 2" of lift with no sacrifice to ride quality ;)

[Eagle]

MJ springs are longer than XJ springs, but the more important difference is that XJs come from the factory as spring-over-axle (SOA), whereas MJs are spring-under-axle (SUA). The MJ springs have considerably more native arch built in, so an AAL that produces 'X' amount of lift in an XJ produces less lift in an MJ.

 

For example, the Rancho catalog lists the same AAL for both the XJ and MJ. It says in the catalog that it produces 2-1/2" of lift. I called Rancho and spoke with their engineering department. They acknowledged that the results are not the same for the XJ and MJ, but the marketing department didn't think anyone would be lifting an MJ so they ignored MJs. The correct spec is 2-1/2" for an XJ but 1-1/2" for an MJ.

 

As for using an XJ main leaf in an MJ, there is simply no way it can lower the vehicle unless you install it upside down (arched against the rest of the pack). In fact, the native arch of an XJ main leaf is about the same as the arch in an MJ pack in the vehicle, sitting with an empty bed. That means adding the XJ leaf would not lower the vehicle, but probably would not lift it very much, if at all. It would, however, add load capacity. In fact, I have a couple of XJ packs that I hope to use for making a home-brew pair of MJ "metric ton" spring packs. My goal is added capacity, decent ride, and no lift.

[500kalle]

Try to find a Not-Worn-out CJ-Leafpack and make your own AALs, you'll get enough Lift AND your XJ will Ride comfortable on The roads and Highways!!!

;-)

[500kalle]

Don't Mount spaces with The Origin Coils, get Granny V8 springcoils!!

[500kalle]

Spacers

[FrankTheDog]

I put a Rustys 3.5" XJ leaf pack in my 92 2wd long bed.

I cut the eyes off the main and took the middle two leaves out of the MJ pack.

Bolted them all together and used a set of Chevy drop shackles.

I gained about 3.5 inches total. Half was from the Chevy shackles.

What I really gained though was carrying capacity.

It's much closer to a metric ton truck now than the cornflake hauler it was.

I almost doubled the amount of weight it can carry comfortably.

The only reason I went with them is because I had them laying around.

[Eagle]

Try to find a Not-Worn-out CJ-Leafpack and make your own AALs, you'll get enough Lift AND your XJ will Ride comfortable on The roads and Highways!!!

;-)

 

I thought CJ leaves were only 2 inches wide ...

 

(Not a CJ guy, obviously.)

[FrankTheDog]

76 and up have 2.5" wide rears.

[mvusse]

MJ springs are longer than XJ springs, but the more important difference is that XJs come from the factory as spring-over-axle (SOA), whereas MJs are spring-under-axle (SUA). The MJ springs have considerably more native arch built in, so an AAL that produces 'X' amount of lift in an XJ produces less lift in an MJ.

 

For example, the Rancho catalog lists the same AAL for both the XJ and MJ. It says in the catalog that it produces 2-1/2" of lift. I called Rancho and spoke with their engineering department. They acknowledged that the results are not the same for the XJ and MJ, but the marketing department didn't think anyone would be lifting an MJ so they ignored MJs. The correct spec is 2-1/2" for an XJ but 1-1/2" for an MJ.

 

As for using an XJ main leaf in an MJ, there is simply no way it can lower the vehicle unless you install it upside down (arched against the rest of the pack). In fact, the native arch of an XJ main leaf is about the same as the arch in an MJ pack in the vehicle, sitting with an empty bed. That means adding the XJ leaf would not lower the vehicle, but probably would not lift it very much, if at all. It would, however, add load capacity. In fact, I have a couple of XJ packs that I hope to use for making a home-brew pair of MJ "metric ton" spring packs. My goal is added capacity, decent ride, and no lift.

 

Maybe I have only seen worn out XJ leaf packs, and non worn out MJ leaf packs, but every XJ leaf pack I have seen not under a vehicle (9 packs from 5 different vehicles, ranging in age from 1990 through 1999) had considerately less free arch than every MJ leaf pack I have seen, including 2 wd ones (10 packs out of 5 vehicles ranging from 1987 through 1990). I lifted the rear of my daughter's XJ 3" by using the XJ main leafs followed by 3 Comanche leafs (some of them cut shorter to fit). I also drilled out the center pin hole in the XJ leaf to match the Comanche ones to use a larger pin to hold them together.

 

With the weight of just the vehicle on it, stock XJ leaf packs are nearly flat. To flatten out MJ springs pretty much takes adding weight until it sits on the bump stops.

[GHayduke]

I threw a 3" Hell Creek XJ AAL in my MJ and got right about 2" of lift with no sacrifice to ride quality ;)

 

I'd be game to try some 3" XJ AALs but I'm having a hard time finding them, as I don't want a full kit, just the leafs. Anyone seen these anywhere?

I've seen a few that don't state a lift amount or application.....

 

Has anyone here tried bastard packs?

 

Thanks for all the good info guys... this is making more sense now! 

[Eagle]

 

MJ springs are longer than XJ springs, but the more important difference is that XJs come from the factory as spring-over-axle (SOA), whereas MJs are spring-under-axle (SUA). The MJ springs have considerably more native arch built in, so an AAL that produces 'X' amount of lift in an XJ produces less lift in an MJ.

 

For example, the Rancho catalog lists the same AAL for both the XJ and MJ. It says in the catalog that it produces 2-1/2" of lift. I called Rancho and spoke with their engineering department. They acknowledged that the results are not the same for the XJ and MJ, but the marketing department didn't think anyone would be lifting an MJ so they ignored MJs. The correct spec is 2-1/2" for an XJ but 1-1/2" for an MJ.

 

As for using an XJ main leaf in an MJ, there is simply no way it can lower the vehicle unless you install it upside down (arched against the rest of the pack). In fact, the native arch of an XJ main leaf is about the same as the arch in an MJ pack in the vehicle, sitting with an empty bed. That means adding the XJ leaf would not lower the vehicle, but probably would not lift it very much, if at all. It would, however, add load capacity. In fact, I have a couple of XJ packs that I hope to use for making a home-brew pair of MJ "metric ton" spring packs. My goal is added capacity, decent ride, and no lift.

 

Maybe I have only seen worn out XJ leaf packs, and non worn out MJ leaf packs, but every XJ leaf pack I have seen not under a vehicle (9 packs from 5 different vehicles, ranging in age from 1990 through 1999) had considerately less free arch than every MJ leaf pack I have seen, including 2 wd ones (10 packs out of 5 vehicles ranging from 1987 through 1990).

 

That's exactly correct. Now go back and read what I wrote.

 

If you take an XJ main leaf, out of the vehicle and out of the pack, and hold it up against an MJ leaf pack IN the pack and IN the vehicle sitting on its wheels with the box empty -- the XJ leaf will just about match the arch of the MJ spring. Since that's the case, it is impossible for an XJ leaf to lower an MJ -- which is what someone else said would happen.

 

Stick the XJ leaf in there, and sitting there with an empty box it won't be doing much of anything -- just taking up space. But ... as you start to add load to the bed, now you have an additional leaf to help carry the extra weight.

[Eagle]

 

I threw a 3" Hell Creek XJ AAL in my MJ and got right about 2" of lift with no sacrifice to ride quality ;)

 

I'd be game to try some 3" XJ AALs but I'm having a hard time finding them, as I don't want a full kit, just the leafs. Anyone seen these anywhere?

I've seen a few that don't state a lift amount or application.....

 

Has anyone here tried bastard packs?

 

Thanks for all the good info guys... this is making more sense now! 

 

Try the Rancho 2-1/2" AAL kit. It should give you about an inch and a half.

[mvusse]

I guess I need to pay better attention to what I read.

 

I thought you were talking about replacing an MJ leaf with an XJ one, not adding it together with the entire original pack.

 

Yes, SUA adding an XJ leaf to the pack will make the springs stiffer, but will add little to no lift. SOA, however, you still at least get the added height from the thickness of the additional leaf.

[GHayduke]

Thanks Guys,  I guess I'm leaning toward the Rancho Add-a-leaf from 4 Wheel Parts: 

 

http://www.4wheelparts.com/Lift-Kits-Suspensions-Shocks/Add-A-Leaf-Kit-Rear.aspx?t_c=1&t_s=101&t_pt=5488&t_pn=ranrs60913&utm_source=google&utm_medium=froogle&utm_campaign=product&emlprox=out&ppcfon=1&gclid=CNS43bHf_7gCFURY3godLB4A6g

 

It's more pricey than some other options at $89, but is a more trusted brand as far as ride quality I think.  I'll see what that gives me with the new C8.25 axle installed.  I can always add a mild shackle lift as needed, should give me some added load capacity as well.  I think it's probablly best to drive the Manche with the lift on it for a couple weeks and see how it settles and what it looks like.  Then I can fine tune the rear height if needed.

 

Any tips for welding the new spring perches on the axle?  Should I try to slam them as low profile to the tube as possible to increase lift? Or will I then not have clearance for the spring pack center bold and hate myself later? I haven't taken a close look at both axle spring perches yet.......

 

I'll try to remember to take before and after pictures and measure too. 

[GHayduke]

I removed my Dana 35 rear axle and installed the Rancho Add-a-leafs with the Chrysler 8.25 axle.  The C8.25 is a half inch bigger axle tube so it will lower the suspension a small bit as it's a spring under axle.  I also don't know in the new axle perch may have been taller...  It looks like in the end I maybe gained a inch total or a little less in the rear .....  

 

 

I'll still be needing to add lift shackles to raise the rear another inch or inch & a half.... not impressed with the lift the springs gave me, but hopefully I'll be better ready to tow now.

 

[GHayduke]

I found some shackles at a swap meet (Jefferson WI) that did the trick.  Factory eye to eye shackle length is about 4-1/4 inches,  I found shackles that are about 6-1/2 inches and installed them.  This gives me about a inch of rake overall and two more inches of hieght at the rear bumper (at least empty w/o gas tank).  I think these were Chevy drop shackles.  I had to grind the frame eye sides down a bit to fit the frame.  I'm a bit concerned that I don't think the leaf spring main eyes moved in the frame during the install, as I used jacks to push the spring eye away from the frame to install the shackles..... :???:   Do you think I need to loosen the main eye bolts or will that not do it?  They may be so stuck they still don't move...  New (to me) Shackle pictured.

 

[JeepsOLot]

With the truck, wheels installed, and on the ground, I would loosen and retorque the frame to main eye, shackle to frame, and spring to shackle bolts, just to make sure the bushings are not twisting, thus destroying them.

 

One thing people forget with lifting SUA is, the thickness of the added leaves in a pack will move the axle away from the spring, thus lowering the truck. We are not talking about much, just the thickness of the added leaves, but, thought I would mention it.

 

Jerry

[FrankTheDog]

The axle sits on the main leaf.

Any leaf that's added is below the main leaf and just adds thickness to the leaf therefore it doesn't lower the truck. The only thing it does is decrease clearance under the springs.

 

The only thing that would lower it is putting blocks between the spring perch and main leaf.

[JeepsOLot]

After working on the springs last night, I realized I messed up, LOL!! Sorry about the wrong info!!

 

Jerry

[mvusse]

 

One thing people forget with lifting SUA is, the thickness of the added leaves in a pack will move the axle away from the spring, thus lowering the truck. We are not talking about much, just the thickness of the added leaves, but, thought I would mention it.

 

Jerry

Ummm, no.

 

The axle sits on top of the main leaf. The rest of the pack including the add-a-leaf sits underneath the main leaf.