I was wondering if anyone has any good reasons as to why nobody does a spring under SAS on Toyotas?  Every thread I have come across quickly dismisses the subject and tells the person to get lost.  But for every spring under thread, there are about 50 threads of people asking how to get their front to sit lower after doing a SAS and high steer.  Don't get me wrong, I know that a traditional SAS and high steer is a very proven and capable system, but it does have it's shortcomings.  These include spring / steering / frame clearance problems, and a pretty severe trade-off between ride height and up-travel.  From what I have seen if you want to keep it relatively low you need to notch into the frame heavily (or start out with a SA / 2wd frame), and you will still only get a few inches of up travel, with at least that much lift in most cases.  So with that being said I would like to start a discussion of the merits and shortcomings of a spring under SAS.  I am not looking to start a hater fest, but I want to take a fresh look at our options for getting rid of the Plague that is IFS.

So here is my case for a spring under SAS:

First of all you would be able to keep it low.  Most spring hangers are designed to give a couple inches of lift by themselves.  Now in going spring under you obviously lose around 5" of lift (if not more) depending on spring and axle thickness.  But now combine the 5" drop with 5" lift springs and a 2" lift from the hangers and shackles, and you end up with a 2" lift.  Now that is not much lift, but for 31-33" tires it would be perfect.  Now not many people can justify a SAS on that small of tires, but it would be nice to have a the option of a solid axle on your DD / parts runner / weekend wheeler.  Now I come from the "cut to fit" school of though on fitting larger tires in most cases, so I am more than fine with minimal lift.  I ran my old '84 4Runner on 36x12.50 TSL SX's on completely stock suspension (actually I had removed the rear overloads, so it might have been down in the back a bit).  The rear fenders were pretty butchered up I have to admit, but the fronts only took a  roughly 12"x8" patch and some finesse with a hammer to make the tires fit with no problems, oh yeah and it had no fenders lol.  I am attaching a pic of the truck as it was.  It rode rough and didn't flex at all, but it could sidehill like crazy (even on the narrower '84 axles) and would go wherever you pointed it.  You literally had to try to roll the stupid thing.

My second reason for spring under is for increased up travel at the previously established low ride height.  I would go to a crossover low steer setup, possibly doing it Chevy "inverted-T" style, or just using heim joints on the stock steering arms, with grade 8 hardware and misalignment spacers on the drag link.  Obviously you would want a beefy tie rod, and would probably want a spare too.  This would keep the steering way out of the way of the springs, and probably allow for stock box mounting and use of a stock drop pitman arm, keeping bump steer to a minimum  Taking rough measurements on my '86 and the axle off of my old 4Runner, I think you could get 4+ inches of travel (steel to steel, no bumps) out of a stock height spring under SAS.  Now figure you have a 2" lift and you get 6" of up travel, which is pretty good for sitting that low.  When compressed it looks like the axle and steering would run out of room at the frame at roughly the same time, meaning that you are not wasting suspension travel because your pesky steering is in the way (or vice versa).  With spring over systems all of the components (and any gaps between them stack up to decrease travel and force an increased ride height at the same time.

Look at the component stackup this way:
Spring Over-
Frame
Steering
Springs
Axle
vs. Spring Under-
Frame
Steering and Axle (same approximate vertical location)
Springs

Pencil the thicknesses of all of these components out and leave appropriate gaps between them and you will see what I mean.

The third and final reason for spring under in my mind is simplicity.  Leaf spring work.  They are not the best, but they get the job done.  Even if they break they can usually be patched back together enough to get off of the trail.  And they are cheap.  The stock steering arms are not super beefy, but they do seem to hold up to a fair amount of abuse, plus every one throws them away, so there would be plenty of spares to go around.

That pretty much sums it up my thoughts.  I know that spring under by its nature decreases ground clearance, but that would be the only major downfall I can think of.  If you made some low profile hangars and kept the axle pad thin you could make it a lot better.  Sorry for the love novel, like I said, I would like to at least give this option an honest look for completely dismissing it.  Thanks for your thoughts.

get lost

   Gotta love that 1st reply, should have known it was coming.

Running flatter springs with the axle under seems simpler. The arch of a 6" won't allow anymore droop than a flat spring and it will ride stiffer. You could run 63" in the back without a block or overload and sit low and maybe a 3" front.
Not trying to to be hater, I just wouldn't build so much just to use some springs I had.

Toyodaaddict, that is pretty much right on the money for what I was thinking.  Looks like he is running a 6 leaf pack up there...would have to add a few to a stock rear pack to get it to sit high enough.  I'm sure I could come up with something out of my piles of extra random leaves.  Dirt Mover, I am not building around springs I have, as I don't have any for the front at the moment, besides if I went RUF with it.  I figured if anything I would just buy 5" front springs and figure on keeping it small for now If I were to do this.  Otherwise are there any non ghetto crossover / low steer setups out there that would be acceptable for street use if a person wanted to do a flatter RUF pack (spring over)?  Anybody else want to chime in?  I thought for sure I would be stirring the pot more than this.

^^How old are your springs? Seems like going negative arch with no bump stops you run the risk of bending a spring or shortening the life of the spring..

Looks like I am going to have a chance to try this out sometime after all.  Just picked up this gem of a 1984 2wd truck.  It is actually much cleaner than it looks in the pic.  I have the full drivetrain out of my old '84 4Runner waiting to go in.  Right now I am planning spring under RUF's, and spring over Chevies in the rear, although I am worried ill be lower than a stock 4wd at that point.  I have also looked at IH scout front springs...narrow, high arched, and there are quite a few in a pack so they should be pretty tunable.  Although with all that arch of the 2wd frame I could just do a traditional RUF setup with high steer and be done with it.  Hopefully I can get started on this in the next month or so as I finish up the garage I have been building.

I know it has been a while, but I think I am going to go for this after all.  My goal here is to keep the suspension at stock height but still have good travel up and down.  According to my stock '86 4wd the center line of the axle is about 2" below the bottom of the frame.  I have my hangers tacked on to the '84 (former 2wd) and the best I can get with a flat to slightly negative pack is axle center line about 5.5" below the frame for 3.5" of lift.  And that is with 4 leaves in the pack.  Add and inch or more with 1 or 2 more leaves in there.  I am going to run a shackle forward setup, which sits slightly higher up than most aftermarket hangers.  It also gives me the ability to have 3 adjustments on my shackle angle.  Ill have to get some pictures up later.  For now I am going to go back out and see if I can come up with a couple higher arch spring packs and mock together some hangers.

I'm seriously considering it.... Have Chilkat steering so soa won't work, thinking going back to springs from links. If I do this I'll do standard rear shackle. Want low cog and stability, drivability and ability to get home if something goes SNAP. Air shocks are nice but I'm always afraid if one goes pop I'm screwed... I have to drive mine to and from the trail...


Sent from magic wish granting phone

Didn't get any pics of it, but I got a 7 leaf pack mocked up which should put me right at stock height.  It looks like I will have about 6" of up travel and 2.5" of down travel.  I would like to see more droop out of it, but need to track down some spring with more free arch to them.  I need to build some spring plates and buy some U-bolts before I can get weight on it, hopefully I can do that tomorrow.

Pics!  I'm guessing you'll get more down travel in real time with articulation forces working for you.

I think it will work. I also think you will be tuning it a bit.  Should handle well for sure.  Really excited to see it sitting on tires though.  Hurry up!

looks good. Nice to see something a bit out of the ordinary.

What made you choose to put the shackles up front? It seems like a bad idea in my mind, mostly from waching jeeps bend springs all the time.  However, Ive heard from a few guys with a lot more knowledge than I, that it can be a good way to go. Im testing it out on my toyzuk project to see for my self.

That was an educational read, definitely backs up what Ive heard.   Your shackle setup does look good and pretty low profile, I like it.

Old topic but I just navigated here several years later...  What became of this spring under venture?
I regret now not picking up a rust free 2wd frame for $500 and instead planning to just patch up the rusted out rear half of my IFS frame... Nice score on the 2wd pickup.  I've got the same bed (sadly minus the hooks), '84 2wd Japanese built bed), for my '88 IFS pickup. 

I was looking at my '84 Toyota axle'd Samurai that's spring over with full high steer kit, and thinking "wow, there really isn't much room to lower this 7.5" lift (over stock SPUA), and a lower center of gravity sure would be nice!" The high steer parts will hit the frame with minimal up-travel if I were to lower it much more unfortunately...
The bigger issue is VW TDI swapping the Toyota axle'd Samurai or the '88, as the more common newer TDI engines will have the oil pan sitting on the high steer SPOA tie rod if you don't go to extremes to shuffle things around.  With the wheelwell position of the Toyotas, it's too much to shove the axle pretty far forward / engine back into firewall without completely moving the wheel arch or butchering up the fenders...

This is when I had the same realization that started this thread.  If I had Front Range Off Road's flat keyed billet steering arms instead of typical high steer arms with 1.5" or so of rise in them, and I had taller arched springs in a spring under configuration, I'd have all kinds of room.  Flat crossover steering arms with spring over axle would put the tie rod and drag link in the same real estate that the springs are in, so that won't work at all, and otherwise that'd be the only way to gain more uptravel clearance. 
Now on the Samurai especially, I'm thinking I'll get a Toyota IFS solid axle swap front spring hanger, extend the front of the Samurai frame a few inches and weld this front leaf hanger across the frame, and do some sort of frenched shackles in the back of the front leafs, or else even some leaf spring slider boxes like what Liquid Iron Industries sells, in case the frame width being narrower than the axle leaf perch width causes too many headaches trying to figure out how to pierce the shackle through the frame when they're not directly on top of one another, the leaf vs frame (leaf outboarded halfway and only under the outer edge of the Samurai frame rail). 
To make this sweeter, a Trail Gear Rock Assault front housing has the axle tubes offset up so the axle shafts are off centered and riding near the bottom of the housing, AND instead of most people's mod of adding IFS hubs to the 81-85 solid front axles to widen them to IFS (and increasing the scrub radius etc), the Trail Gear Rock Assault front housings add 3" to the passenger side, so you can run the 81-85 style hubs and have proper scrub radius, but still have the IFS width stance.  They include the passenger side longer than stock axle shaft with the housing, FYI.
The other HUGE perk to that Rock Assault housing, is that by offsetting the axle housing tubes up to gain more ground clearance, it also allows us more lift if doing an unconventional Spring Under Axle, as the leaf will mount higher up off the ground with the bottom of the tubes up higher off the ground... AND... additionally, if the leaf perch is no longer sitting at the edge of the differential housing where the perch has to be lower with more stacked drop height off the axle tube, since the passenger axle tube is 3" longer and the leaf mounts on the tube clear of the diff 3rd member housing, you get the leaf mounted higher again....  I was going to do '88 Toyota Old Man Emu 2" lifted rears up front and '89 Toyota Old Man Emu 2" lifted rears out back with a long wheelbase OEM Samurai body panel assembly for about 25" longer cargo bed in the Samurai, + frame stretch...  I can do sheetmetal work to make the wheel arches larger diameter and higher up, and move the LWB rear wheel arch a few inches back as well, and that'll allow 33" 255/85R16 Interco TrXus M/T Radials to stuff nicely under flex with 16x7 wheels...

I'll chime in here - my truck is currently SUA. You can find details in my build thread. It's not good. If you go SUA, you must swap to shackles in the front like the OP did. Simply put, with shackles in the rear the front half of the spring is too short and at too steep of a downwards angle. This creates a lot of brake dive, like it sits on the bump stops when I touch the pedal. I've patched this up by adding air shocks that are really providing most of the front spring rate at this point, but ultimately I'm going to be three-linking the front end when I have the time.