SOA vs SUA

OK, I did a search but I couldn't come up with anything, I'm just curious as to which you guys would suggest. I want to lift my Jeep enough to get 35's under it, and I'm wondering if I should go SOA (lots of lift for not much $$) or if I should stay SUA with lift springs and probably shackles. Are there any inherent advantages/disadvantages to either one. Oh and gearing with the 35's wont be a problem... my Jeep's brutally low geared as it is, so 35's should be perfect!

Thanks........Wil.

 

My choice in this case would be SUA. You're going to need to replace the shackles anyway so go with bigger, beefier ones.

 

Huh. IMO SOA would be a huge mistake unless you have lots of experience with suspensions and welding. Your gearing is not so low - your crawl ratio is about 25, and again IMO you're not going to see any major advantage with the 35s and a big lift over, say, 31s or 32s with a 2" lift. Plus raising your COG that much is going to make the Jeep much less stable on the street.

 

Brakes? you have to stop them once you finally do get the 35"s rolling

 

Lynn pointed out you have 4.27s. I didn't catch that earlier. That is not low gearing imo. That is what I have and I'm running 33s. I still felt the need for the t18a with the granny gear. I have been very happy with the 33s on my jeep. I do have top heavy issues now though. It doesn't seem quite as stable as it did with the 31s. With such a short wheel base the 33s keep me from getting hung up most stuff. If you buy a decent lift kit they typically come with axle shims of varying degrees. Some even come with the dropped pitman arm. I didn't need to do that to mine but you might. Another thing to consider is your horsepower. The bigger the tire the more horsepower it takes to move it. You may not have the luxury of muscling your way out of a bad situation with the set up you're talking about. I don't mean to be preachy, it just sounds like you are starting in a similar place I did with mine and I made a few mistakes before I got to where I am happy with it.

 

Good point! I have disks on the front and now that I have 33s I wish I had them on the back too.

 

Spring over axle turns out to be much more expensive when you figure for the high steer and longer everything. Plus, you will have to deal with a lot more axle wrap. Plus, the way your Jeep sits now, you could probably fit 35's. Lot's of room in those wheelwells. Is there a lift on there now??? Body lift.

High5

 

I had 12.50-35's several years go just did it cause they were there and a good deal. Had 33's the 35's were just enough taller to make cog really squirlly after I got up to speed. Had enough engine and 5.38's so i really didn't notice any change there. But with narrow trac axles found it really not real useful for what I did with it. Young guys thaought it looked really cool though. Also snapped axle when I had 'em went back to 33's after that.

 

JP just did an article in last months issue about the real cost of SOA. Lets just say after all the stuff that has to be done I don't see an advantage. But looking at the numbers everyone is giving unless you like to swap out clutches your gearing is going to be way to high for 35s.

 

Actually I do have experience welding, and I'm turning 2600 rpm at 60, and 35's would knock it down to about 2100 rpm. I'm working on power brakes, I was simply wondering if anyone here has done SOA and wished they'd stayed SUA and put lift springs instead.

 

I agree with everyone else, I would stay spring under. You will regret 35's and 4.27 gearing. Your motor is actually geared good now. Any bigger tire and you will be lugging that motor to death on the trail, especially since the dana 20 you have has a poorer low range than the dana 18 does. Now if you put a tera low kit in the transfercase that would help significantly. My .02¢, YMMV!!

 

I guess I'm odd. I've got 3.73s and 36 right now. Of course my crawl ratio is 74-1 so thats not bad for wheelin.

What exactly do you plan to do with those 35s? If you are into rockcrawling etc... then I would say go SOA, but you need to think of the whole system and not just put the springs over the axle. If you just want it higher or do general trail riding then I'd follow everyone elses suggestion and stay SUA with possibly smaller tires. For most situations staying SUA and having 33s is perfect.

Spring lift kits are fairly cheap. Last time I looked they were roughly $500-$600. That was a while ago, but not a bad deal for a whole suspension system. To do SOA correctly can get very expensive. Keep in mind you may not even reuse your old springs and your gonna need a bunch of parts to finish it anyways. Plus you might as well go wider while your at it and that means new axles, blah, blah, blah.

So the real question is, what do you plan to do with it?

Kevo

 

Well the thing is, I want taller gearing. The engine screams at 60 mph, and 35's are cheaper than an O/D tranny (once you factor in adaptor plates, etc...), and easier to do than a gearing change, there's also the benefit of having more tire surface area than 31X10.50's. I can't afford to go all out and I don't want full width axles (I think it looks ugly), and I don't plan on changing the springs. Just putting the spring pads on the top of the stock axles, a dropped pitman arm, longer shocks and brake lines.

 

35s will only gain you one inch over 33s.
Stay SUA and run 33s.
Alot less involved and you can buy a complete sytem for less than $600.
2600 rpm is not screaming.

 

35's would gain me 1" in tire radius and ride height, however there is
6.28" difference in tire circumference (so with each revolution of the tire the vehicle will go 6.28" further). SUA may be less involved however I have the ability to do SOA (and I don't have the money for a SUA lift kit). Maybe I wasn't clear about my original question, I just want to know if SOA would make the Jeep handle worse than with SUA (assuming that the Jeep was lifted SUA and sitting at the same height as with the SOA) And 2600 for an hour continuously everyday is a bit much... I have to almost hold it floored on the freeway to do 60.

 

To do a SOA correctly you will have at least that much money if not more. New springs, shocks, brakelines, driveshaft mods, building a track bar. Plus all the brackets, spring perches, shock tabs, ubolts. Not to mention the time doing it. Then there is also the chance of the caster being too far off in the front, and having to have the knuckles turned. A simple aftermarket kit can be put on in a couple of hours where to do the springover your looking at a lot of time depending on how fast you work.
Not trying to discourage you but its not just as simple as bolting the springs to the top of the axle. And depending on what springs you use yes it will make it much more unstable unless you rig up some sort of sway bar.

 

Please do yourself a favor and read the latest JP, they discuss the real cost and it is not cheaper by a long shot. It might seem cheaper but after you add in new springs, correct steering setup( no bent draglinks), new shocks, new bumpstops and several other things it is not cheaper at all. Heck even Extreme 4x4 had an episode showing that really it costs quiet a bit of money to do springover correctly, and they skimped in a bunch of placed I personally would not have.
2600 is not bad at all, heck our ZJ does 2450 down the highway all the time. The problem you might incounter is that you will need that speed to keep your RPMs in the powerband.

 

Hey Wil- I hope you don't feel like you're getting beat up by everyone but the info you've received is pretty much right on the button. SOA is going to be a lot more squirrely than SUA unless you've got the time and $$$ (part of your reason to want SOA) to build and experiment with your own custom leaf packs until you get exactly what you want.

I hate to say this but 2600 isn't excessive at all. If you have to almost hold your foot to the floor to keep it at that RPM, your Jeep IS NOT going to like having the extra stress of 35's. It probably won't be able to power your Jeep at highway speeds in top gear- more likely you'd have to run in a lower gear at a higher RPM to keep the same speed. Any 258 should be able to easily power a Jeep with 33's and 4.27's. If you need a ton of throttle to get it to 2600 RPM, you've probably got one seriously tired engine or it's waaaay out of tune. I hope I'm not adding insult to injury but I dream of the day my Jeep would be able to cruise at highway speeds @2600. Won't happen till I can afford an overdrive and even that might be a stretch. Most auto mfr's design their vehicles to cruise at highway speeds (55-65mph) at the RPM which produces the most torque which equals peak fuel economy since the engine requires a minimum of throttle opening. This figure usually falls between 2200 and 2600 RPM FWIW.

Whatever you decide to do, good luck with your project!

 

Regarding the highway performance, I wonder what you expect. In my experience, all the intermediates, even with a 232, are quite easy to drive on the highway. Your 258 has a peak torque at about 2000 rpm, and peak power at 3500 rpm. That puts your top speed at about 80 mph, which should be fast enough. It's true that a Jeep sounds like it's working hard compared to a passenger car, but that's the nature of the beast. There's no insulation between you and the drivetrain, and typically there's a lot of tire noise. If you think you've got noise, you should drive a Dana 18 equipped Jeep... the Dana 20 is used because it's a "silent" design, even though it has an inferior low range. I put carpets in my Jeeps, with extra padding underneath - helps a lot.

Your comments also make me wonder whether your engine is really tired, since a 258 moves a CJ along just fine. You're so lucky to already have 4.27s in your axles - in my experience they are fine on the street, and should give you better performance on the highway, not worse.