Leaf Springs and the Axle - JeepForum.com

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post #1 of 8 Old 04-13-2010, 03:34 PM Thread Starter
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1990 YJ Wrangler 
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Location: Texas
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Leaf Springs and the Axle

I've noticed on some Jeeps the leaf springs are a lil diff than mine. I've wondered if it's just the YJ-way or what.
But the axle is above the leaf springs. I've seen some where the axle is sitting below the leaf spring.

To me, it makes sense for the axle to be below the leaf springs. But I'm just wondering, and wanting to see what people think, and have you guys done anything about it.

Plus, my leaf springs are getting old, 20 years old, so they need replacing soon. So whenever I go to replace 'em how should I put 'em back in.

Open in any opinions, please post. :]

Thanks :]

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post #2 of 8 Old 04-13-2010, 03:39 PM
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Not sure what you are looking for. Search SOA and SUA and I'm sure you'll find lots of info related to the different suspension configurations people are using. There is also some info in the FAQ.
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post #3 of 8 Old 04-13-2010, 04:00 PM
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The stock configuration for all YJ's was to have the springs under the axles. Many people do what is called an SOA or (Spring Over Axle), there are a good deal of benefits to going SOA but you should know that it is not simply welding some new spring perches above the axle. There are a number of things that have to be addressed, like a Slip Yoke Eliminator for the transfer case, which brings the need for a new rear drive shaft, longer brake lines, longer shocks, addressing steering related issues, there's a lot to be done and it's not real cheap. Read, read, read, that's the best advice I can give you on that.

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post #4 of 8 Old 04-13-2010, 04:04 PM Thread Starter
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To make it shorter and less complicated-

My leaf springs are under my axle, are they supposed to be there? I've seen it differently in other Yj jeeps (leaf springs over axle). If I replace them, (which I am very soon since they are 20 yrs old) should i put them over the axle instead?

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post #5 of 8 Old 04-13-2010, 04:08 PM
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That's the stock configuration, they're supposed to be that way. If you replace your springs and leave them that way it's a fairly easy thing to do.

As bgred mentioned, there's no easy answer to whether you should go SOA (springs over axle) or stay SUA. Google it and search the forums for SUA and SOA to get the pros/cons and an idea of the process.
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post #6 of 8 Old 04-13-2010, 04:46 PM
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The YJ's came from the factory with the springs under the axle (SUA). Lift springs, or even factory replacemnt springs are intended to put on in the same way (SUA).

If you want to put the spring on top of the axle (SOA), it can be done, and will give close to 6" of lift on factory springs. As well as a better ride (as compared to lift springs) and more flex. However, doing an SOA conversion is not cheap, easy, or quick. There are a lot of things that need to be done to do it safely. Your driveline angles will need to be adressed with a slip yoke eliminator (SYE), a new CV drive shaft will need to be made fro use with the SYE, an anti wrap bar for the rear axle is a must, and steering correction for the front axle will need to be done.

This will require a decent amount of knowledge and skills to do, as there is a lot of welding that will need to be done. When going SOA you will be doing it to fit bigger tires. The D35 rear axle doesn't like 33" tires and will break easily. So you will want to consider a ford 8.8 rear axle swap at the time. Since your going with bigger tires and a stronger axle, you should regear the axles too since you will have them out. 4.88 is very common for 35" tires.

Just what wrote above will run you close to $2k. More or less depending if you can do the work yourself.

Look in the FAQ section at the top of the YJ Tech forum. Under suspension, there is a great write up on doing an SOA and links to other SOA related stuff, including why not to do it on the cheap.

Get comfortable, and have a seat. You will want to do hrs of reading before you pick up a wrench. The more knowledgable people here have made some very costly mistakes, and have posted them here so that others can learn from them. Head the warnings posted by others and do your research. It will pay off big dividens if you do.

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If it has tracks, tires or tits, its gonna cause a problem.

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92, 4.0, AW4, 8.8, D30, 15x10, 37's, SOA etc, etc
92, 2.5, 30, 8.8, 4.88, Locked, Winch, 15x8, 35's, 3.5" (RIP)
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post #7 of 8 Old 04-13-2010, 04:58 PM Thread Starter
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I'm just gonna stick to factory ways..

Thank you guys for posting!
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post #8 of 8 Old 04-13-2010, 05:57 PM
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You do not require a SYE or new axle for SOA.

It is always a good idea to replace the D35- but that can be done for around $120 for an 8.8 around here.

My buddy is SOA, with a D35 (he has an 8.8 already waiting for the d35 to break- he has been waiting 3 years) he wheels hard, and no SYE. No vibes, and no issues with Ujoints. No body or MML either. Just a tcase drop. Depends on the jeep.

SOA is a good conversion, just do it safely.

"A man has to know two things in life, limitations and priorities. You let your priorities get in the way of your limitations." - MrBlaine
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