SAS Swap - Dumb question(s)!

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SAS Swap - Dumb question(s)!

Postby furiousbob » Sun May 02, 2021 12:54 am

So I'm getting ready to SAS my 90 Trooper. First time doing an SAS.

I just picked up a 83 Toyota front axle today with a high steer kit. Going to rebuild it, slap some 4.56's in and ARB the front and rear at the same time.

I was driving the axle home today and thought to myself, how does the front diff driveshaft mate to the where there used to be 2 CV's? Am I missing something? :shock:

Edit :: I MUST be missing something here. I've been driving for 14 hours. I'm going to bed. Someone clear up my stupidity.

------------------------------------------------------------------------------------------------------------

EDIT EDIT :: Can't sleep, I might as well turn this thread in to my preliminary planning thread

So for the fronts, I'll be fabricating shackles and hangers. I'll need to purchase strut towers, struts, leaf pack ( Yota or Zu? ) and I'll worry about the driveshaft later on.

The front will be SOA, shackle forward as suggested by other members and it'll have the aforementioned high steer kit mated to a red-top steering box. Unsure about pitman arm compatibility but I'll research more.

For the rear, it'll be Zu 12 bolt with hopefully, an ARB locker. I'll convert it from SUA to SOA to try and match the front and I'll adjust accordingly via more fabricated shackles and/or AAL. For the conversion, I can just cut the spring pads off and weld new ones on the top, right? I'll need extended struts as well.

Am I missing anything?

------------------------------------------------------------------------------------------------------------

Oh also, front geometry. I know this is pretty critical. I'll need to research more before posting my plan.
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Re: SAS Swap - Dumb question(s)!

Postby Enemigo » Sun May 02, 2021 1:59 am

What geometry specifically? If you're going with leafs instead of links and coil springs, you should hopefully have less to deal with.
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Re: SAS Swap - Dumb question(s)!

Postby mudoilngears » Sun May 02, 2021 9:47 am

The whole CV shebang goes. All you use is the driveshaft. That would gon
straight from the transfer case to your new axle.
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Re: SAS Swap - Dumb question(s)!

Postby furiousbob » Sun May 02, 2021 10:42 am

Enemigo wrote:What geometry specifically? If you're going with leafs instead of links and coil springs, you should hopefully have less to deal with.


I guess there's not much to it. Specifically, the rake. I thought about it since more and all I would do is measure the rake with the IFS relative to say, the fenders? And then keep that position with the SAS.

Otherwise the track would just be symetrical with the frame and pinion angle would be measured with the suspension compressed. I think I'm good!
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Re: SAS Swap - Dumb question(s)!

Postby furiousbob » Sun May 02, 2021 10:44 am

mudoilngears wrote:The whole CV shebang goes. All you use is the driveshaft. That would gon
straight from the transfer case to your new axle.


Ok that's what I was thinking. I was going to crawl underneath and take a look but I'm assuming there's a trans axle or something that goes from the transfer case to the CV axles that gets removed and then I'd just have to figure out a driveshaft.
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Re: SAS Swap - Dumb question(s)!

Postby mudoilngears » Sun May 02, 2021 10:48 am

furiousbob wrote:
Enemigo wrote:What geometry specifically? If you're going with leafs instead of links and coil springs, you should hopefully have less to deal with.


I guess there's not much to it. Specifically, the rake. I thought about it since more and all I would do is measure the rake with the IFS relative to say, the fenders? And then keep that position with the SAS.

Otherwise the track would just be symetrical with the frame and pinion angle would be measured with the suspension compressed. I think I'm good!

Caster is what you have to worry about.
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Re: SAS Swap - Dumb question(s)!

Postby furiousbob » Sun May 02, 2021 10:26 pm

Oh boy we're going down the rabbit hole. Been doing lots of reading on old threads. Chuffer seems to have the most experience with this swap. He uses rear trooper springs for his front but I'd rather find an alternative since I've already welded some stuff forward of the frame

I still have lots of reading to do. Has anyone used rear rodeo springs?

Also, is SOA ok with a high steer crossover? I read that SOA's have issues with frame interference. How would one mate a crossover steering linkage to the pitman arm? Weld the pitman arm in and re-ream it?
Last edited by furiousbob on Mon May 03, 2021 12:28 am, edited 1 time in total.
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Re: SAS Swap - Dumb question(s)!

Postby mudoilngears » Sun May 02, 2021 11:10 pm

Trooper and Rodeo springs are the same.
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Re: SAS Swap - Dumb question(s)!

Postby furiousbob » Mon May 03, 2021 12:27 am

Great!

Thanks!

I'll need to evaluate my options. Or I'll probably just end up extending the frame.

Spent the day cleaning up the donor axle.

Taking my time with this. I'll start the rebuild some time this week.

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Re: SAS Swap - Dumb question(s)!

Postby paulevans76 » Tue May 04, 2021 5:13 pm

What vehicle, what size tires are you aiming for, and how is the rig going to be used?

SOA front is going to end up sky high, just FYI. I mean like 9-10" of lift. But the high steer will need that clearance to keep from hitting the frame. If you have a manual, your front driveshaft is likely going to be a huge PITA because it will be short and very steep at ride height.

Warning - unsolicited advice below! :mrgreen: :blackeye:

If it was me and I was going to run leafs front and rear, I'd swap the front to SUA, use a crossover steering set up - either Y-link to the stock tie rod mounting location, or with the drag link running to a high steer arm on the pass side only (and you'll probably still be fighting for clearance with the frame). With trooper springs or waggoneer 2" lift springs SUA in the front, and a rear SOA, you'll clear 35's or larger on a 1st gen trooper depending on trimming you're willing to do. It will be like 5" over stock which is plenty. More than that, and things get tippy!

Personally, I'd either run shackles forward to make many things easier, taking a small approach angle penalty, or run fixed eye front and a set of slider boxes instead of shackles in the back (liquid iron industries makes a set targeted at hardcore wheelin') - you'll keep from getting the shackle hung up on stuff, and you'll keep the spring eyes closer to level, which will help with brake dive, caster, handling characteristics, and driveshaft slip. You could use slider boxes in the shackles forward scenario too if you wanted.

Another thing - 4.56's are going to be pretty miserable, even if you went with 3:1 in the case. Maybe if you have a diesel or v8 they would be ok, but I'd be looking at 5.29s for the front, and either swapping in a toyota rear or finding some 5.38's for the zu 12 bolt, or a dana 44, etc etc.
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Re: SAS Swap - Dumb question(s)!

Postby Enemigo » Tue May 04, 2021 6:06 pm

Do you have friends with experience with this helping you out?
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Re: SAS Swap - Dumb question(s)!

Postby furiousbob » Tue May 04, 2021 7:07 pm

paulevans76 wrote:What vehicle, what size tires are you aiming for, and how is the rig going to be used?

SOA front is going to end up sky high, just FYI. I mean like 9-10" of lift. But the high steer will need that clearance to keep from hitting the frame. If you have a manual, your front driveshaft is likely going to be a huge PITA because it will be short and very steep at ride height.

Warning - unsolicited advice below! :mrgreen: :blackeye:

If it was me and I was going to run leafs front and rear, I'd swap the front to SUA, use a crossover steering set up - either Y-link to the stock tie rod mounting location, or with the drag link running to a high steer arm on the pass side only (and you'll probably still be fighting for clearance with the frame). With trooper springs or waggoneer 2" lift springs SUA in the front, and a rear SOA, you'll clear 35's or larger on a 1st gen trooper depending on trimming you're willing to do. It will be like 5" over stock which is plenty. More than that, and things get tippy!

Personally, I'd either run shackles forward to make many things easier, taking a small approach angle penalty, or run fixed eye front and a set of slider boxes instead of shackles in the back (liquid iron industries makes a set targeted at hardcore wheelin') - you'll keep from getting the shackle hung up on stuff, and you'll keep the spring eyes closer to level, which will help with brake dive, caster, handling characteristics, and driveshaft slip. You could use slider boxes in the shackles forward scenario too if you wanted.

Another thing - 4.56's are going to be pretty miserable, even if you went with 3:1 in the case. Maybe if you have a diesel or v8 they would be ok, but I'd be looking at 5.29s for the front, and either swapping in a toyota rear or finding some 5.38's for the zu 12 bolt, or a dana 44, etc etc.


Thanks for chiming in, Paul! I've been reading all your old threads on the topic.

This is being done on a 90 Trooper. Aiming for 35" tires and truck is used mainly for camping and wheeling. Not a daily.

I realize now that a SOA is going to be ridiculous. I'll need to chop off the pads and weld new ones on for a SUA. I do have a 5spd.

I appreciate your advice!!

The axle came with a crossover setup. It's got a y-link, I believe. If you look at the photo above, you'll see a tie rod attached to high steer arms and then there's a separate steering rod off-screen.

I'm not super familiar with the steering components. I've run IFS all my life, after all hah. I may need to revisit steering after I've rebuilt the front axle.

I believe I'll be going with trooper springs. If I go this route, I'll need to mix and match leaves for proper height/clearance, right?

Shackles will be ran forward. I've reinforced the section in front of the frame ends previously to support a winch. I'll need to cut that out and extend the frame.

Gears... well it's pretty much impossible to find anything for the Zu. I figured 4.56 would be ample for the yota axle. With 35's... maybe not. I had a chance to pick up a rear toyota axle too. Dang it. Maybe I'll keep looking.

This project's going to stretch out. My landlord just told me to cut out the welding. I may have to move first since I make a chunk of my income off of fabrication.
1990 Isuzu Trooper 5MT
Reproduction round-eye grille w/ Hella E-Codes
Home-made front/rear bumpers w/ Smittybuilt winch + KC Daylighters
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Sway-a-way HD Torsion bars cranked 1.5" higher
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Re: SAS Swap - Dumb question(s)!

Postby furiousbob » Tue May 04, 2021 7:08 pm

Enemigo wrote:Do you have friends with experience with this helping you out?


I do not, unfortunately. I have a buddy with a K5 but he comes to me for all his truck needs haha.

Most of my other friends are investing all their time in their families or their kids.
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Sway-a-way HD Torsion bars cranked 1.5" higher
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Re: SAS Swap - Dumb question(s)!

Postby paulevans76 » Tue May 04, 2021 9:08 pm

This is a doable swap for sure. Probably the most labor intensive part is getting rid of the IFS and cleaning up the frame. Black boogers, fried forearms, it's a lot of fun! Then it's just a lot of measuring and mocking and crossing fingers (and watching where you put em) and tacking, measuring, etc. If your landlord is telling you to cut out the welding, yeah, it might be better to put it off until you aren't worried about making a lot of noise.

F250 shock mounts (can't remember what year, but some google or searching the old pirate forums will help) are cheap and good if you want something fairly off the shelf.

Keeping it SUA and only lifting it as much as you need it to clear your tires is going to keep things like your front driveshaft a little easier to work with. You may be able to get away with ditching the high steer arms and running the OE steering arms (low steer) if the drag link angle isn't too steep. Chuffer also had a pretty cool steering setup on a yota axle to try and deal with the lack of clearance to the frame

It will be a bit of a dog with the 4.56s but you can just pinch some pennies until a pair of geared toyota 3rd members pop up for sale. 35s and a manual with 4.56s is driveable, just not ideal, especially in technical stuff. I did 35's and stock gears in an old rig for a long time because I was on a non-existent college student budget.
Scratch n Dent special 1991 Trooper S
3.4 V6 - Holley TBI, CompCams 252H, 1.6:1 roller rockers, +1mm DOHC pistons, MSD ignition, custom tune, "Ed Mc Special" 2.5" exhaust
MUA5 w/ 3.07's & fixed yoke
SAS - Waggy F D44 - 5.38's, RCV's, OX locker; Rodeo R 44 - Detroit, truss
Front Y-link radius arms, coils; Rear SOA, OME leaves, anti-wrap bar
35x12.50/17 General Grabber X3's on 17x9 Interco Birddogs
Trail armor and Warn XD9000
The White Whale - a temporary daily driver 1991 Trooper - 2.8 V6, MUA5 - stocker resto (sold)
1994 Samurai - 1.3 FI - OME suspension, 31's, 6.5:1 tcase, 5k milemarker SxS winch, more to come!
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Re: SAS Swap - Dumb question(s)!

Postby furiousbob » Tue May 04, 2021 9:20 pm

Oh yah I'm looking forward to cutting and welding underneath. That's the best part! I'm glad it's not as daunting as I made it seem in my head.

The F250 shock mounts, I'm well aware of. I'll get a set. We use these on everything and anything that needs shock mount replacements haha.

Are there issues running all this on the stock steering gear? I went through an ordeal a while back with crummy reman units and ended up splurging on a red-top. I'm hoping I don't have to get rid of it.

What do most people do about adapting the steering linkage to the pitman arm? Weld shut and drill/ream for the new steering linkage ball joint?

I think I'll have to keep looking for a toyota rear, then. As far as that goes, it seems pretty straightforward:

1) Toyota rear is already SOA, IIRC?
2) Can I machine a pinion adapter to make the factory driveshaft work with the toyota axle?
3) I've heard that you need a 1 piece driveshaft when lifting the rear that high?
1990 Isuzu Trooper 5MT
Reproduction round-eye grille w/ Hella E-Codes
Home-made front/rear bumpers w/ Smittybuilt winch + KC Daylighters
1" Body lift, 1.5" lift Indy4x shackles
Sway-a-way HD Torsion bars cranked 1.5" higher
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Re: SAS Swap - Dumb question(s)!

Postby paulevans76 » Wed May 05, 2021 9:55 am

Are there issues running all this on the stock steering gear? I went through an ordeal a while back with crummy reman units and ended up splurging on a red-top. I'm hoping I don't have to get rid of it.
What do most people do about adapting the steering linkage to the pitman arm? Weld shut and drill/ream for the new steering linkage ball joint?

The main issue is that the stock pitman arm is a little short - but it may be ok for toyota steering arms. You basically want your pitman arm length to match your steering arm length to get full throw and steering. The next issue IIRC is that the zu arm has the rod end go in through the top. There's an F250 or something with a similar enough taper to work in the stock location, but ideally, you'd just drill it out from the bottom to either GM taper or the toyota taper and run it up through the bottom of the pitman arm which helps with angles as well.


I think I'll have to keep looking for a toyota rear, then. As far as that goes, it seems pretty straightforward:
1) Toyota rear is already SOA, IIRC?

Correct. I would think about investing in an anti-wrap bar for the rear. Barnes and Ruff Stuff make pretty affordable kits.

2) Can I machine a pinion adapter to make the factory driveshaft work with the toyota axle?
IIRC, maybe 2 of the (edit) bolt holes in the isuzu flanges line up on the toyota flange and you might be able to drill the others, but not sure on the centering ring. Probably best to machine an adapter to use toyota ujoints (capable of 42* as a single joint, and there's also a stock CV that will do 37* IIRC) at least for the front where you will need that additional angle. You can be old school budget and make a square tube shaft for the front to save some bucks if high speed vibes aren't a concern. If you'll need the 4wd at speed on the road in the snow or something, then pony up for a balanced shaft.

3) I've heard that you need a 1 piece driveshaft when lifting the rear that high?
Absolutely - good to do anyway. 2 ways you can start: You can go ahead and swap to a fixed rear flange on the tcase (from a rodeo) or you can leave the slip yoke. As long as it's not lifted to crazy, the slip yoke should work fine - it shouldn't need a ton of slip to go through the range of motion. Then, take a look at the 2nd gen trooper shafts - I don't know if it's the auto or 5speed but a few guys have found that they work and bolt straight in a 1st gen. Either swapping the slip yoke onto the 2nd gen ujoint, or if you have done the fixed yoke swap, you just bolt it in. At least with the 12 bolt - you could measure to be sure the overall length is right, and then just take the shaft to a machine shop or driveshaft shop and have them put a toyota joint on the axle end and be done with the rear.
Scratch n Dent special 1991 Trooper S
3.4 V6 - Holley TBI, CompCams 252H, 1.6:1 roller rockers, +1mm DOHC pistons, MSD ignition, custom tune, "Ed Mc Special" 2.5" exhaust
MUA5 w/ 3.07's & fixed yoke
SAS - Waggy F D44 - 5.38's, RCV's, OX locker; Rodeo R 44 - Detroit, truss
Front Y-link radius arms, coils; Rear SOA, OME leaves, anti-wrap bar
35x12.50/17 General Grabber X3's on 17x9 Interco Birddogs
Trail armor and Warn XD9000
The White Whale - a temporary daily driver 1991 Trooper - 2.8 V6, MUA5 - stocker resto (sold)
1994 Samurai - 1.3 FI - OME suspension, 31's, 6.5:1 tcase, 5k milemarker SxS winch, more to come!

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