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· 3 Leaf Fab
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The intention of this thread is to put together all the related information in a concise manner that is easy to understand and does not take 15 pages of reading to gather all of it. This will be geared more toward people that are unfamiliar with the process of converting to solid axles. Most of this info does not even have to be s10 specific but is typical of any solid axle swap. The information in this is not intended to be a how-to but rather to get you to think of all that is involved and to point out the commonly overlooked or under-considered aspects of the conversion.

Reasons to go SFA:
It is my opinion that while a SAS is not for everyone, it is certainly a benefit in several key areas that deal with any lifted trucks. By my reckoning, there are three main reasons to swap in a solid axle. The first is that solid axles offer the potential for more strength of components. While a dana 30 is roughly similar in specs to the stock IFS diff, the nature of the solid axle makes the difference. The second reason to swap in a solid axle is to get more lift. IFS lifts top out at 6”, which only gets you to a 33”-35” tire even after you factor in body lifts. S10s with solid axles typically run 12” of lift or more (which sounds like more than it really is). The third reason to swap in a solid axle is to get the components that larger solid axles provide, namely larger brakes and bearings. Larger tires mean more rolling mass and inertia, and the stock components are just not up to the task of stopping safely. If you do any towing with your truck, then this is doubly important. Also, the larger and wider the tire becomes, the greater its leverage over the wheel bearings. Solid axles, especially dana 44’s and larger ones, offer a larger size and spacing of wheel bearings that can deal with larger tires more safely. This third reason is enough, in my opinion to put a sofa in a daily driver, especially if you run 33s or larger.

Things to consider:
While converting to SFA is simple in concept, it can be difficult without the proper knowledge or skills and can be very frustrating without proper planning. If done right, the actual conversion can be done in a weekend, provided you have all the tools and parts ready. Also, while the conversion can be cheaper than buying some of the IFS lift kits, there are small things that will add up to make the cost more than just a set of axles and tires. This article will cover more of what is needed later.

Where to start:
When trying to figure out what a build will need, I like to start with what tire size I would like to run. This will to some degree, determine how much lift I need and what level of strength I need for all the components. I would think that 33s are the minimum tire that an SFA build should use, and it goes up from there. Use tire size as a starting point for picking out the front axle you want to use. Three axles are generally used in this swap, the Dana 30, Dana 44, and Dana ’60s. As a general rule of thumb, Dana 30’s can survive 33-35’s. Dana 44’s can go up to about 38’s. anything larger would be a Dana 60. Remember that this is just a guideline and that other aspects of the build will change these numbers. Along with the front axle, every build will or at least should be replacing the rear axle as well. The largest reason for this is to get a matching bolt pattern for the rims. There are no solid front axles that have the s10 bolt pattern. There are more choices for rear axles, but the common ones are Dana 44’s, ford 8.8 (equivalent to the Dana 44), ford 9”, Dana 60’s and 70’s, and GM 10.5” 14 bolts.

The next major choice is what type of suspension to build. Some prefer leaf setups for their easy fabrication and lack of geometry needed. Some like link suspensions because of the control and flexibility they offer. Let me just state right now that within typical setups, both links and leaves offer the same amount of articulation, and neither is better than the other in general. Each type will offer benefits that the other cannot, but this is more of a matter of preference.

Leaf suspensions:
Probably used more in the typical SAS, leaf suspensions will consist of a pair of leaves and shackles, a fabricated front cross member and a pair of mounts for the rear end of the spring. The two big choices are where to place the shackles and what length of springs. There are many debates on putting the shackle in the front or rear. Most, however, choose to run the shackle in the rear, and the largest reason for this is its high-speed driving characteristics. When shackles are run in the rear, the suspension movement allows the axle to swing back as it goes over a bump. Front shackles force the axle to move forward into the bump as it goes over it, which results in a harsher road ride. Front shackles, however, have the main advantage of allowing the pinion axle to tip up as the suspension cycles, which helps save u-joint life. Rear shackles tip the pinion down as the suspension cycles, which exacerbates the angle seen by the u-joint. Almost all leaf suspensions will use a 31.5” center-to-center spacing on the leaves, which matches a large majority of leaf perches that axles come with. Going narrower is an option to some degree which can help clear the spring mount on the inside of the frame rail, but at some point, the leaf perch would have to start climbing the differential housing, which makes mounting the spring difficult. Going wider with the springs can give you greater stability, but at some point, the tire will start rubbing the spring at full lock, with can limit the turn radius of the vehicle. Most applications will also utilize a spring-over design with the spring on top of the axle tube instead of under it. This is generally done just to get more lift than spring under. Low lift conversions may consider spring under, especially since it simplifies the steering linkage.

Link suspensions:
Link suspensions have an aura of mystery about them that is not truly deserved. Link suspensions that we use in offloading applications are not the same as link suspensions used in race cars, which is where all the math and terminology come from. I will not get into depth on how to set up a link suspension, but I will give an overview of basic types and benefits. When dealing with front suspensions, almost every application will have a Panhard bar because this is needed to reduce bump steer caused by the axle moving side to side as the suspension cycles. The ideal Panhard bar is run parallel to and as close to the drag link as possible, and both should be as flat or level as possible. The further away from this ideal, the more bump steer there will be. An upper frame mount for the Panhard will need to be fabricated. All S10s with link suspensions are going to need a mount for either the coil or a more sophisticated spring. You can reuse the factory upper shock mount (I did), or you can fabricate another upper shock mount. Beyond this, there are three basic choices for links. The simplest form of link suspension is the radius arm type. This is what 70’s f-150 front suspensions used, and some might consider just using a modified form of the ford design. Radius arms, in concept, are the same as a four-link where the frame ends of the upper and lower links converge at the same point in space. Some jeeps use a “long arm” kit which is really just radius arms with a fancy name. A benefit to both the “long arm” and the ford style is that you can use the existing mounts on the axles and just fabricate the frame mounts. You can also just modify factory or aftermarket arms to suit your needs. Another benefit to the radius arm design is that as the axle drops, the pinion keeps its relative angle to the radius arm, which helps to keep at least the lower u-joint at a healthy angle. Wristed radius arms are a slight modification to the design, and they are sort of a hybrid between radius arms and a true three-link. They are like having an upper and lower link converge at the same point on the frame on the non-wristed side and having just a single link on the wristed side. The next basic link design is the true three links. In a true 3-link, the upper link frame mount is in a different location than the lower links, which gives the axle, among other things, an amount of pinion rotation that is dependent on the geometry. One potential benefit to this design is the ability to tune the pinion angle to that both the u-joints in the front drive shaft stay in alignment with each other. The other effect of having a true three link is that you have the ability to design in squat/dive or anti-squat/anti-dive. In basic terms, when you apply to throttle, the energy created by the drivetrain does not fully propel the vehicle forward. A portion goes into the suspension, either loading or unloading the springs. Both of these can be desirable effects depending on driving style, terrain, and preference. In a suspension that trends towards squat, when you apply power, the geometry loads the springs and that end of the vehicle drops. In an anti-squat trending suspension, the vehicle would raise. The leaf spring analogy of this is the axle wrap that can occur under hard acceleration or braking. Since the theory is that links will not bend into an S shape as leaves will, the vehicle has to raise or lower instead. By the way, if any were using the online calculators to figure out the geometry, 100% squat is neutral, with less trending towards squat and more toward anti-squat. The last basic link design is the four links, but this is really just an extension of the three links, with two links sharing the load the upper link sees. 4 links provide more control but may take up more room on the axle or frame. An example of this four-link is the factory suspension in a jeep or dodge. This is not the same as a triangulated four-link used without a Panhard bar. There are also more exotic link designs, but these were the basics.

How much lift:
In a sense, the springs chosen will determine the amount of lift that you will get. There are many different choices of springs to choose from, both leaf and coil, from many stock and aftermarket sources. My personal choice is to use stock springs from other applications. The two basic reasons for this are cost and spring rates. Stock springs tend to be much cheaper as they can be found in junkyards and off-donor vehicles. They also tend to have softer spring rates than aftermarket springs though this has changed in the last few years as the aftermarket has started to shift towards softer rates. But the main idea I want to convey is that you do not need “lift” springs to get a lift. The amount of lift is a function of how they are mounted to the frame and what they provide over the stock setup. My build used rear springs from a stock 88’ f150 4x4. When used with the frame mounts I had, I got roughly 12” of lift from them. This amount of lift sounds like a lot, but because the trucks start so low, to begin with, it is deceptive. My blazer with 12” of lift and 38’s could still drive under a typical garage door, and I think the roof was only at about 85” from the ground. This is about the same as a stock 4x4 super duty. My rear coils were from an XJ front suspension, though in hindsight, they could have had a slightly higher spring rate. In the end, there is no formula for determining exactly how much lift is required for each build. My advice is to jack up the truck and sticks the new tire size under it, then measure and decide how much lift you want to run and what springs will get you there. You can also decide at that point if you want to modify the wheelbase and deal with what that entails.

Prepping for the build:
Converting to SFA will disable your vehicle for a certain amount of time, which is dependent on how much prep work you do. Things such as cleaning the new axles, re-gearing them for larger tires, adding traction devices, etc., can all be done beforehand. I recommend inspecting any seals and bearings during this phase because it will never be any easier than when the axle is out of the truck. While having bare housing is easier to manipulate due to simple weight, it can add downtime to the build, which may be a factor for some. Gathering all the parts needed before can also save time so that you are not running down to napa every couple of hours because you forgot to get all the parts. I also recommend having a complete parts list to keep it all organized and to keep track of how much you are actually spending on the conversion.

Parts list:
This list is typical of many builds, but applications may vary. Some parts may not need to be replaced but should be inspected.
  • Front axle
    • New gears and installation kit
    • Traction device (locker or similar)
    • Seals and bearings (don’t forget the inner seals)
    • Axle shaft u-joints (and trail spares)
    • Rotors, callipers, and pads
    • New lockout hubs or similar
    • New wheel studs
    • New lug nuts (always an overlooked item)
    • Heavy duty diff cover?
    • New ball joints
  • Rear axle
    • New gears and installation kit
    • Traction device (locker or similar)
    • Seals and bearings (don’t forget the inner seals)
    • Disk conversion parts (Rotors, new or donor callipers, and pads)
    • New wheel studs
    • New lug nuts (always an overlooked item)
    • Heavy duty diff cover?
    • Provisions for parking brake
  • New rims to match the new lug pattern (don’t forget to consider backspacing)
  • Tires (don’t forget a spare)
  • Steering
    • Astro box? (moving the axle forward?)
    • Pitman's arm
    • Drag link with DREs or TREs
    • Heavy duty tie rod
    • Flat top knuckle?
    • Steering arms
    • Hydraulic assist?
    • Steering stabilizers (not needed, in my opinion)
  • Extended brake lines
    • Proportioning valve for rear disks?
  • Extended length shocks
  • Driveshafts
    • Rear drive shaft (don’t forget to factor slip length)
    • Conversion u-joints?
    • Front drive shaft (don’t forget to factor slip length)
  • T-case
    • Rear SYE
    • Front fixed output
    • “HD” planetaries
    • Doublers?
    • Manual shift t-case?

The old suspension:
Once you get your parts together and any prep work done, then you can start on the actual conversion. You will need to remove all of the old suspension components and diff mounts. An oxy-based torch does quick work of this but is careful not to damage the frame itself. Be sure to leave the shock tower if you plan to reuse it. WARNING: When you remove the lower control arm mounts, you will be removing a portion of the frame that ties the two sides of the frame together. I would recommend adding a brace before you remove this section. The front-leaf cross member can act at this point, though, in my opinion, only if welded on. If you run links or a bolt-on leaf cross member, I would recommend adding another frame brace above or below the engine to keep the frame from separating due to the engine. The front bumper is not a substitute for this, in my opinion.

Transmission cross member:
Most builds will need to replace or at least modify the transmission cross member. The factory setup has the front driveshaft going over the cross member, which is great when the front differential does not move relative to the t-case. But with the lifts and high articulation involved in the conversion, the drive shaft at rest typically has to occupy the space the factory cross member takes up. Don’t forget to account for up travel of the front drive shaft. I would recommend having a bolt-in cross member to ease any t-case or transmission removals.

In some cases, you may need to make changes to the exhaust system to clear the drive shaft or other components that you are building into the system. Keep in mind how the axle and other components move as the suspension cycles to keep the exhaust clear of these areas. You will also want to keep in mind how close to the floor or other areas you run the new exhaust and what effect the heat will have on the things around it.

Vacuum system:
When removing the old components, you can keep the stock vacuum actuator and just unhook the cable. You can also remove these items as they will not be reused and can be a potential vacuum leak source. If you remove these components, forget about the vacuum lines going to the t-case and be sure to plug any open vacuum lines.

The popular thing is to run dual t-cases. This is very helpful for a rock crawler but is not essential and is certainly not for every build. There are a few things to consider, though, if you want to run dual cases. First, you will need to either run a body lift or modify the shape of the floor (at least in a blazer). The stock floor is formed around the contours of the first t-case but does not allow for the second case. Consider also the amount of length that you will be adding to the front drive shaft and removing from the rear drive shaft. In short wheelbase applications, you may want to run a double cardan-style shaft. Remember to properly support the assembly's weight and not solely rely on the factory trans mount. Also, remember that the additional gear reduction makes it all the more likely that you will need to have stronger parts downstream, such as u-joints and axle shafts.

Engine swaps:
While sometimes a reason for the conversion, swapping the engine is not a needed step in converting to a solid axle. It is, however, probably the most convenient time to swap the engine as you are likely to have the front end half torn apart anyways. Doing it at this time also allows you to plan both swaps around each other to maximize space and effort. Just remember that swapping in a heavier engine will impact what springs to use for the front suspension.

Steering is an often overlooked or undervalued aspect of converting to a solid axle. The steering system will consist of three major components; the steering box, the drag link, and the tie rod. The stock s10 steering box will if there is not too much lift or the front axle is not moved forward too much. If either of these is present, consider using an Astro steering box. There are a few differences between the two, but the major ones are the fact that the Astro box has the pitman arm forward and the s10 box has it pointing backwards. Using the Astro box also lets you run less of a drop pitman arm to help keep the steering load within the strongest alignment. As for pitman's arms, there are several you can use. I chose to use a ford 4” drop arm. Part of the process for picking out components is deciding which TRE or DRE to use. I will let you research which of these is the best, but I recommend using a TRE and not a Heim's joint. Plenty of people run Heims and do not have any issues, but they are typically designed to run in double shear and not single shear like most steering joints. TRE, due to the taper, is designed specifically to run in single shear. Either way, I recommend running the drag link directly to a steering arm and not to the tie rod. The biggest reason for this is that running the drag link to the tie rod typically limits you to a few factory-style TREs that have a location for a slaved TRE from the drag link. These types of TREs are not the strongest and should be avoided for any vehicle with more than mild off-road use. Several aftermarket companies sell steering arms that mate up to dana 44 and dana 60 flat-top knuckles, and I think there are aftermarket knuckles for the dana 30 that accept the drag link. Tie rods can be run off the factory knuckles or up higher with a set of high steer arms. I would recommend using tubing that is at least 1.5” OD x .25” wall for all steering components and larger if you run the tie rod in the normal position and like to rock crawl. Mine were made from 1.5” OD x .375” wall.

Below is a list of links that have been condensed from other threads related to the conversion. Btw, on virtually all the threads, the credit belongs to other people for finding the info; I just compiled it.

List of SFA builds
SFA Newbs, check here before posting
Axle Specs
Dana 30 cross-over steering write up
Solid Axle Thread
Manual Shift 233
233 Fixed output shaft
297x joint info
hydro assist info
Dana axle BOM numbers
axle lists
transmission shifting while in low range
t-case info
no case numbers explained
s10 brake lines to jeep axle adapter
gear ratio calculator
wiring info
manual shift 233
more manual shift 233
t-case guide
info on steering geometry and pinion angle
233 output shaft swap
axle specs

Build threads:
Below is a list of some of the build threads by members of the board. Sorry if I did not like your build.
friend of DieselS10
friend of crew cab rabbit
crew cab rabbit
ride harder
HP Addict
92 s-dime
mog-10 portal axles
4wdjoey’s $300 rig
Snafu pimp

· Registered
3,604 Posts
Damn. This needs to be the top stickied and closed. Pretty much sums up any question I had before I started mine...

· Life's too short for IFS
752 Posts
This has to be by far the best, most complete source of SAS info for these trucks Ive ever seen in one place. A great addition to our community, Sticky for sure. Thanks Donahue!
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