Information overload. Help!

[The Jester Race]

I am getting ready to do a leaf sprung SAS on my 87 BII using fullwidth Dana 44 and Dana 60 axles from a 79 F-250. I have been reading as much as I can about SAS's, and the more I read the more questions I have.

First question, regarding front pinion angle. The front axle has a spring perch cast into the diff. If I use the stock spring perches I assume that I will have a good pinion angle and caster angle. Am I correct in assuming this?

Second question. What is more important, pinion angle or caster angle? Can you change the caster without affecting the pinion angle or visa versa?

Third. When all is said and done, and I am setting the alignment, what do I take the alignment specs from? The BII or the F-250?

Fourth. Rear pinion angle?

Spring arch vs. shackle length vs. spring length? What are some of the front leaf spring setup you guys are running?

Thats all I have for now, but Im sure there will be more.

Thanks

-Jester

 

[4x4junkie]

Chances are pretty good you'll be fine reusing the stock perches already on the axle, but the angle your leafs are mounted at can affect the outcome of this (try to maintain the same angle the leafs were mounted at on the F-250).

Caster angle is FAR more important than pinion angle up front. If you have to sacrifice one for the other, sacrifice your pinion angle to get proper caster.
To change the pinion angle relative to caster angle, you'll need to cut the welds holding the inner knuckles off at the ends of the axle tubes, then rotate the inner knuckles whatever degrees are needed, then reweld them.
Use the alignment specs for the axle you're using (F-250).

Are you going to use a double-cardan or single-cardan rear driveshaft? (this matters for your rear pinion angle).

 

[The Jester Race]

Thanks 4x4junkie, the plan is to use a double-cardan drive shaft, hopefully the same one that I had built to replace the CV style shaft if its long enough.

With the spring perches parallel with the ground(0*) the caster is a little less the 1*, so I'm guessing its about 0.7* or 0.8*. and the pinion angle is 6*.

Does that sound about right? Seems kind of on the low side for caster, isn't it?


-Jester

 

[4x4junkie]

Yes, you want to have somewhere between 3-6° caster (sounds like the F-250 sloped it's springs back a little bit (rear spring eye a little lower than the front spring eye), which is actually pretty common on leaf-sprung vehicles.

 

[The Jester Race]

How much lower does the rear eye have to be to gain 1* in caster? Is there a formula for it, or is it a trial and error type thing? Im just really dreading having to grind out that cast perch from the housing.


-Jester

 

[4x4junkie]

Unless you can find some specs (or a whole complete truck to measure from), gonna have to do some trial-&-error.

Don't forget you can also adjust things by the length of your shackles, and there are also wedge-shims available that you can put on the bottom of the springs to adjust it a few degrees as well.

 

[The Jester Race]

Alright, Thanks for your help 4x4junkie. Ill have to look around and see what I can come up with.

I have a question about springs now. I can get a set of new Rancho springs for the rear of a wrangler for about $50. They have a spring rate of 200lbs, and a free arch of 7.25". But they are a tapered spring, so I cant do an add-a-leaf, or re-arch them.

I am looking to get about 6" of lift for the front, and looking at it at 8 O' clock at night and holding it next to my BII it looks like it would be close.

200lbs, too soft? Too stiff?

Any thoughts?

Thanks


-Jester

 

[4x4junkie]

I would think those would be about right.

Not sure what you mean by tapered, If it's just the very ends of the leaves that are tapered (pretty common, actually), you should be able to still add or pull a leaf.

 

[The Jester Race]

They are .25" thick in the center of the spring and taper down to .09375" at the ends. They are Rancho RS44150 springs.