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With any significant amount of lift in a V8 powered FSJ, you can get into bad operating angles on the front driveshaft very quickly. While an SOA is a (relatively) simple way to gain clearance for a lot of tire - it is almost a guarantee of front driveshaft issues.
However - most of the front axles that you will find from non-FSJ applications are set up for SOA. So what do you do then? Well, it is entirely possible to do a little grinding and weld perches on the bottom of your GM, Dodge, or Ford axle - but then you still have the 'hooks' underneath your truck's front axle ('hooks' in this case refers to stuff that will hang you up on obstacles, like your u-bolts and such).
In an effort to maintain decent front driveline angles, lower center of gravity, and make use of the least expensive donor axle sets, I have been trying for a long time to come up with a solution to combat the height of most SOA setups. I have come up with a pretty good answer, which I will share here.
Dodge truck front leaf springs.
Here's the thing; Dodge front leaf packs have the rearward eye wound UNDER the spring, instead of above it - this moves the main leaf 2 inches (roughly) closer to the frame than a stock (or most normal) leaf spring pack. Coupled with the fact that most Dodge front leaf packs are 3 fairly thick leaves actually makes them a thinner pack thickness than the 7-leaf FSJ front packs. The thinner pack reduces the height from the SOA slightly. Also, the Dodges sit flat or slightly negatively arched under load, again bring the axle CL closer to the frame - limiting the amount of lift.
It is also nice that the Dodges are a thick main leaf which should be less prone to bending than the stock FSJ main leaves.
The downside is pretty minor - the eye-to-eye length is 48" instead of 47".
If you want to keep your shackle in the stock location and do the Dodge spring swap with the least amount of work, move the rear hanger of the front spring back on the frame 1". In order to do that, get some 3/16" by 1" steel. Cut 3 pieces 2" long. Use one piece of 3/16"x1" as a 'spacer', and the other 2 as 'stops'.
Hold or clamp the spacer behind one spring hanger tight against it and square with the frame rail. Place the first stop behind the spacer, tight against it and the frame, and weld the stop in place. Break the spacer free and repeat the procedure on the other side. Now you have a solid location for the spring hangers that will be exactly equal when the work is done.
Cut the heads off the rivets with your favorite implements of destruction - but DO NOT mangle the hanger. Also, remember to cut the weld on the inboard side of the hanger where it meets the frame rail. (remember; you are reading all of this on an internet forum - so use any of this information at your own risk, don?t just hack into your truck's suspension because of what some crackpot el-cheapo said on the internet)
Once you get the hangers off the frame, grind everything nice and flat on the frame and the hanger so they will go together nicely when you put them back on the frame. You are a grown up now, so no booger welding over slag or faking it or welding through rust flakes. Take a little time and prep the area well.
Installation is reverse of removal. However - the Dodges use 1/2" bolts instead of 9/16" - so make some 1/8" or 3/16" thick plates to use as washers which you can tack to the mounts and shackles. It probably wouldn't be a problem with just washers - but better safe than sorry.
The first truck that I have done this on has turned out really well - I will try to add some pictures soon. Next time, I will likely move everything FORWARD a little and do a shackle reverse, with the shackle bushing through the frame, and use a fixed front mount. Or, move everything forward by putting the shackle ahead of the front crossmember.
However - most of the front axles that you will find from non-FSJ applications are set up for SOA. So what do you do then? Well, it is entirely possible to do a little grinding and weld perches on the bottom of your GM, Dodge, or Ford axle - but then you still have the 'hooks' underneath your truck's front axle ('hooks' in this case refers to stuff that will hang you up on obstacles, like your u-bolts and such).
In an effort to maintain decent front driveline angles, lower center of gravity, and make use of the least expensive donor axle sets, I have been trying for a long time to come up with a solution to combat the height of most SOA setups. I have come up with a pretty good answer, which I will share here.
Dodge truck front leaf springs.
Here's the thing; Dodge front leaf packs have the rearward eye wound UNDER the spring, instead of above it - this moves the main leaf 2 inches (roughly) closer to the frame than a stock (or most normal) leaf spring pack. Coupled with the fact that most Dodge front leaf packs are 3 fairly thick leaves actually makes them a thinner pack thickness than the 7-leaf FSJ front packs. The thinner pack reduces the height from the SOA slightly. Also, the Dodges sit flat or slightly negatively arched under load, again bring the axle CL closer to the frame - limiting the amount of lift.
It is also nice that the Dodges are a thick main leaf which should be less prone to bending than the stock FSJ main leaves.
The downside is pretty minor - the eye-to-eye length is 48" instead of 47".
If you want to keep your shackle in the stock location and do the Dodge spring swap with the least amount of work, move the rear hanger of the front spring back on the frame 1". In order to do that, get some 3/16" by 1" steel. Cut 3 pieces 2" long. Use one piece of 3/16"x1" as a 'spacer', and the other 2 as 'stops'.
Hold or clamp the spacer behind one spring hanger tight against it and square with the frame rail. Place the first stop behind the spacer, tight against it and the frame, and weld the stop in place. Break the spacer free and repeat the procedure on the other side. Now you have a solid location for the spring hangers that will be exactly equal when the work is done.
Cut the heads off the rivets with your favorite implements of destruction - but DO NOT mangle the hanger. Also, remember to cut the weld on the inboard side of the hanger where it meets the frame rail. (remember; you are reading all of this on an internet forum - so use any of this information at your own risk, don?t just hack into your truck's suspension because of what some crackpot el-cheapo said on the internet)
Once you get the hangers off the frame, grind everything nice and flat on the frame and the hanger so they will go together nicely when you put them back on the frame. You are a grown up now, so no booger welding over slag or faking it or welding through rust flakes. Take a little time and prep the area well.
Installation is reverse of removal. However - the Dodges use 1/2" bolts instead of 9/16" - so make some 1/8" or 3/16" thick plates to use as washers which you can tack to the mounts and shackles. It probably wouldn't be a problem with just washers - but better safe than sorry.
The first truck that I have done this on has turned out really well - I will try to add some pictures soon. Next time, I will likely move everything FORWARD a little and do a shackle reverse, with the shackle bushing through the frame, and use a fixed front mount. Or, move everything forward by putting the shackle ahead of the front crossmember.
EDWARD! EVER EDWARD!
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