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Question about SOA leaf conversion for front axle


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EDIT: I guess the title should be more specific to the question about converting the front to leaf springs. Pardon my inaccurate problem description. 

 

I am kind of new to the off-roading modification scene. I am wondering what the deal is with people doing leaf conversions on the front end (SOA conversion, is that the term?) I've done a little bit of reading on the forums but cannot get a clear understanding.

 

I don't understand the benefits or why someone would do it to their Comanche. I see it sometimes on Wranglers, and honestly with Wranglers the benefits seems more intuitive. But I'm curious about the Comanche. To me, it seems like it would drastically reduce articulation and turning radius (unless your wheels are sticking out a ton).

 

I guess, specifically, I'm hesitant to buy a local Comanche that is for sale because it's got this SOA conversion on the front and I know nothing about. Seems like a ton of welding and whatnot, although it looks like it was done well. Says it's got Dana 44 and 60 and then 4" YJ leafs on the front. Is this front-end leaf conversion a normal thing?

 

Just looking for some last-minute insight. Thanks much! 

 

These are the pics on the ad (you post it on the internet it becomes fair game, right  B)).

 

 

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SOA actually stands for (Spring Over Axle). It doesn't specifically have to do with front or rear, just weather or not the suspension is leaf sprung, the other option is SUA (Spring Under Axle). Our comanches are leaf in the rear and control arms up front, same as a cherokee.

 

Judging by your sig you have both a cherokee and a comanche, if they are both stock, your cherokee should have SOA, and your comanche SUA, take a look :)

 

also a reason why one would go SOA over SUA, at least on our truck, is that it's a cheap way to get around 5 or so inches of lift. (there's a bit more work though...and welding)

 

I hope this help, I also hope I'm right :P

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I think that the OP is referring to putting leaf springs on the front axle in place of the factory quadralink.

 

This is not uncommon when upgrading to heavier duty axles as they are usually wider. It is sometimes simpler to adapt leafs to the frame than the stock suspension to the axle. As the pics you posted show you can get very good articulation out of leaf spring suspensions.

 

My big concern with buying such a converted rig is just what you mentioned: the quality of the fabrication. If I had someone whose knowledge and experience allowed them to give me a good opinion that it was OK I would buy one if the price was right.

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I think that the OP is referring to putting leaf springs on the front axle in place of the factory quadralink.

 

Yeah, pretty much that's what I meant to ask. To me it just seems so over-kill to convert the front to leaf springs with all the modification that would be needed, as opposed to just doing the standard lift with keeping the coil springs like most people do.

 

I guess I was wondering why people do that and if it's good/bad? Or is this case just an anomaly? 

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This is not uncommon when upgrading to heavier duty axles as they are usually wider. It is sometimes simpler to adapt leafs to the frame than the stock suspension to the axle. As the pics you posted show you can get very good articulation out of leaf spring suspensions.

 

My big concern with buying such a converted rig is just what you mentioned: the quality of the fabrication. If I had someone whose knowledge and experience allowed them to give me a good opinion that it was OK I would buy one if the price was right.

 

I see. Thank you for the explanation. Supposedly over $5k was invested in the suspension (parts and labor), so I was just surprised on such a huge investment on such an old vehicle and wondered why so much! 

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If you look at the flex in those pics you could argue that leafs are not really such a step backwards. Sometimes the location of the diff housing or things like radius arm mounts make mounting the factory coil buckets and control arm mounts difficult.

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I was wondering the same thing.  Why down grade to leaf?

 

I'd be weary about buying someone else s project, unless I knew exactly what I'm looking at.

 

Ahh, see - the fact that you consider it a downgrade makes me curious about these sort of modifications. I hope to talk with the guy in the next 10 hours or so. Thanks for input.

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Sure doesn't look like a downgrade from the pictures. Sounds like he put a strong axle in and decided to go with leaf springs instead of coils. Potential downside would be ride quality. If I'm honest, my mj rides like crap anyways. It's a truck, it should ride like one. If the work was well done and you have all the information on Tue parts used for future maintenance, and you're comfortable with the price, I say it looks like a mean truck.

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Sure doesn't look like a downgrade from the pictures. Sounds like he put a strong axle in and decided to go with leaf springs instead of coils. Potential downside would be ride quality. If I'm honest, my mj rides like crap anyways. It's a truck, it should ride like one. If the work was well done and you have all the information on Tue parts used for future maintenance, and you're comfortable with the price, I say it looks like a mean truck.

this

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The big advantage to a leaf spring setup is simplicity. Your axle is only attached to the chassis by two leaf springs. A coil spring setup like the XJ/MJ one has five links doing the same job. You're looking at much less design work, much lower cost, much easier repair, etc.

 

The big disadvantage to a leaf spring setup is handling precision. Lateral and longitudinal axle location as well as caster are controlled by springs, which means there's some give in every direction. Five reasonably rigid links will keep the axle much more constrained than two intentionally flexible ones will, leading to much better on-road performance.

 

Obviously that isn't that big a concern for a rig that spends most of its time at relatively low speeds on unpaved unroads. Even in a daily driven pavement pounder, there are few scenarios where racecar-sharp handling is absolutely necessary, but it is incredibly nice to have the comfort of knowing that your vehicle will perform in the event of an emergency.

As has been said, going from coils to leafs is a cheap, easy, and reasonably effective way to swap in a beefier axle; especially if the desired axle is already set up for leafs. This is assuming of course it's been done properly. Making sure the vehicle will safely take the load at the new spring attaching points is particularly important with a unibody chassis.

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This is a very clean MJ and it has had a ton of work, the swap was done by a shop in southern Oregon and they did a very poor Job.

 

Since then the rear axle has been rehung with a Ruff stuff swap kit and has a proper driveline angle.

Originally the front had the shackles on the frame side and the pinion angle was so far out that the truck hasn't had a driveline since the swap, the front axle had to be realigned and recentered, the shackles have been replaced with liquid Iron slider boxes to rotate the axle back to fix the pinion angle.

It may require a high angle CV but it should accept a front drive shaft.

 

 

The truck drives pretty much exactly like a SAS toyota, it's not bad but its not like a linked MJ.

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The same guy still owns it, not sure why he hasn't kept up the build thread.

 

He did end up doing the AX15 swap as well as a SYE and a custom rear drive shaft.

It's too bad what happened to this truck.The shop that did the work ripped him off and gave him back a barely driveable truck, he called us a while back and said the truck was on the side of the road in Portland, it axle wrapped so hard that it shattered the drive shaft which flipped around and ripped a hole in the gas tank.

 

We towed it to our shop and put in a new tank and had a new custom shaft built for it, we also addressed a bunch of serious issues from the build, the front axle was mounted so far off that the wheelbase was about an inch off from side to side,one front fender is damaged due to the axle being too far back on one side.

 

We took the axles out and redid alot of what the original shop did,everything is staight now and the truck goes down the road as it should, we were going to do a bunch more work to it and we had talked about eventually converting it back to links.

 

The main issues currently is the brakes and the axles, the builder hooked the 3/4 ton brakes to the stock master and booster, they work but not very well. The axles are right out of a 79 F250 and the rear has leaking axle seals, it is also badly in need of tires.

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If you look at the flex in those pics you could argue that leafs are not really such a step backwards. Sometimes the location of the diff housing or things like radius arm mounts make mounting the factory coil buckets and control arm mounts difficult.

Considering the the Wrangler YJ was leaf spring all around and had a lousy reputation for articulation, and that Jeep's solution with the TJ Wrangler was to go to coils on all four corners, I see no benefit to converting a front coil suspension to leaf springs. I think a good long-arm suspension kit would be far superior, for a lot less money.

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Having flexed this truck in person I can say that the flex is not that impressive,I had 4 MJs here at the time and this one had the least flex.

 

Its got very stiff YJ lift springs up front and MJ lift springs in the rear, we lowered the truck a little but its still sitting around 9" of lift.

 

It's really too bad the shop did the leafs. The front axle that was used is about as good as it gets for a link swap, very long short side and tons of room to put everything.

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If you look at the flex in those pics you could argue that leafs are not really such a step backwards. Sometimes the location of the diff housing or things like radius arm mounts make mounting the factory coil buckets and control arm mounts difficult.

Considering the the Wrangler YJ was leaf spring all around and had a lousy reputation for articulation, and that Jeep's solution with the TJ Wrangler was to go to coils on all four corners, I see no benefit to converting a front coil suspension to leaf springs. I think a good long-arm suspension kit would be far superior, for a lot less money.
That was largely due to ignorance and a fear of change on the part of those with "conventional wisdom" at the time. In time it turns out that the flat leaf springs of the YJ work well and it is now recognized that flat leafs are desirable. The TJ went to coils to address ON road driveability/ride comfort and increased safety/litigation concerns rather than off road performance. As mentioned above by another poster link suspensions are far superior on road.

 

A guy I wheel with put full widths under an xj and went to leafs in the front. Using used FSJ springs and hangers from Barnes he claimed to have about $200 in the front suspension. I don't think you can do a link suspension on axle swap for a lot less than $200. The most common way to do the leafs is shackle hangers sleeved through the subframe for the rear mounting point and attaching the springeye mount to a simple fabbed front cross member. This guy used a length of 4x4 square tubing. It also seriously tightened up the front end.

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It's too bad what happened to this truck.The shop that did the work ripped him off and gave him back a barely driveable truck, he called us a while back and said the truck was on the side of the road in Portland, it axle wrapped so hard that it shattered the drive shaft which flipped around and ripped a hole in the gas tank.

 

We towed it to our shop and put in a new tank and had a new custom shaft built for it, we also addressed a bunch of serious issues from the build, the front axle was mounted so far off that the wheelbase was about an inch off from side to side,one front fender is damaged due to the axle being too far back on one side.

 

We took the axles out and redid alot of what the original shop did,everything is staight now and the truck goes down the road as it should, we were going to do a bunch more work to it and we had talked about eventually converting it back to links.

 

The main issues currently is the brakes and the axles, the builder hooked the 3/4 ton brakes to the stock master and booster, they work but not very well. The axles are right out of a 79 F250 and the rear has leaking axle seals, it is also badly in need of tires.

 

This is a lot of really useful information  :thumbsup: And I'm really surprised someone knows the details of this build so well. Thanks mnkyboy. You say "were going to do a bunch more work to it" so I assume the owner just sort of dropped the project. Maybe it became a money pit. I hope to get in touch with him this weekend. 

 

I don't know, it seems really sketchy to me that someone would take such a clean, low-mile truck and jack it up 10 inches like that, and so poorly too (not blaming the owner). Kind of a shame. But to each his own. So that's why I asked the question about this leaf conversion in the first place. 

 

I don't know about axles seals on the MJ, but I think on the Grand Cherokee they are a pain to replace.  

 

Thanks for the helpful info guys. 

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His build started out on the right track then he talked to the shop and they convinced him to build it how it is. you wouldn't believe how much money he has in this thing,he is losing his @$$ on the truck if it sells.

 

We got it driving good then we were going to address the brakes and axle seals, It's got a 79 Ford full float D60 in the rear so axle seals are fairly easy.

 

The owner ran into some problems and is forced to get rid of the MJ, otherwise he would still be building it.

 

I think its been for sale for a little while now but it sat at the shop till about a week or so ago.

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