Pro / Con of SOA or SUA?

[lcoutback]

I'm converting my '89 Pioneer 2 wd to 4 wd.  Staying with the Renix for now, with an AW4/231 swapped in from an '89 XJ.  I already have 4.5" coils, drag link and adjustable upper/lower control arms from an old XJ project.  From what I've read (and what my trusty Stanley 25' tape measure tells me) I should get roughly 5" lift on the rear by merely doing a SOA conversion with new spring pads.  I see a good number of builds on this sight that stayed with spring under. 

 

This is going to be my daily driver, with only occasional desert and logging trail off-road exploration.  I have Dana's from a 2000 XJ that are getting 4.10 gears so I can run 33's like I had on a previous XJ.

 

I would appreciate input from fellow MJ drivers on SOA vs SUA, and why?

Edited December 30, 2017 by lcoutback
typo

[Pete M]

both methods will work just fine.    more often than not the choice seems to boil down to things like price or condition of the OEM leaf packs rather than some sort of concrete advantage of one over the other.  

 

 

[SBpunk]

both methods will work just fine.    more often than not the choice seems to boil down to things like price or condition of the OEM leaf packs rather than some sort of concrete advantage of one over the other.  
 
 

Spring under has less of a chance for spring warp but there are things you can do to prevent it. It also allows easier access to the bed specially for daily drivers. You can get cheap WJ control arms up front to clear 31s and don't have to worry about adjustables.

Spring over you get the higher lift. Usually comes with bigger tires which means bigger brakes, longer control arms, shocks, coil springs, steering etc.

Honestly for a DD I'd stay under until you're ready to upgrade everything.

Sent from my PH-1 using Tapatalk

[Pete M]

WJ arms won't be long enough for a 4.5" lift

[SBpunk]

WJ arms won't be long enough for a 4.5" lift

Good call missed that part.

Sent from my PH-1 using Tapatalk

[Eagle]

I don't think you can do an SOA conversion and keep it to 5 inches. Most people seem to get 5-1/2 inches or more.

 

[Incommando]

I went SOA.   As I was swapping in an 8.25 as part of my 2wd to 4wd conversion anyway it was the easiest way to achieve the rear lift.  I went with “anti-wrap” spring perches from Barnes 4wd and have never had a spring wrap issue  on or off road. On road manners are fine. With your 4.5” front springs you can use front spacers of varying heights to get the front stance that you want.  

[lcoutback]

Thanks for the feedback!

 

I've been leaning toward SOA, since the spring packs are in great shape. (No rust, sits even, truck was mostly a grocery getter, so no sag to speak of)

 

I have front end components from an XJ (not an MJ) that I've used before.  I'll likely do the rear first, then buy new coils to get me as close to the same lift as the rear.  I'll be putting new brake lines, booster conversion, etc to keep it safe AND fun!

 

@Incommando - thanks for the suggestion on the antiwrap perches.  I'm (mostly) past my hotrod days, but better safe than sorry!

[DesertRat1991]

One main advantage of SUA is that helps lower the COG of the vehicle. A low COG is useful offroad and when using your MJ to do truck stuff (i.e. hauling). 

 

For a vehicle designed to support up to a metric ton over the rear end, the engineers probably figured it was a good idea to keep the COG as low as possible.

[ParadiseMJ]

The only reason I'd go SOA is the shock mounts and pack running so low to the ground bugs the hell out of me.  I'd be happier just slimming it ^up.   For me, I like the road manners of my 3.5" SUA lift and 30" tires.  I know doing an SOA is a fairly straight job, but to me, it's not worth spending the extra $$ getting all the front end parts.  I learned on my first XJ after I lifted, locked and chopped it up, when I was done I hated it.   I hated it so much I gave it to my son who breaks stuff offroading and fixes it monthly.  IMHO, unless you use it regularly for wheeling a mild lift and good tires makes for a 200% better ride.