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Discussion Starter · #1 ·
So I have a bone stock 90 RC with the TBI 318,
When I bought it It tracked horribly and the ball joints were obviously worn. I replaced everything (all ball joints, all tie rod ends, steering box to knuckle connection), after an alignment it ....... tracks horribly!
The original upper ball joints had offset bushings and the technician rolled them around to achieve +1° caster on the left (drivers) and +2.1° on the right. (+.01 camber left -.01 camber right, .12 toe in left and .10 toe in right)

Since it still tracks so badly I would like to achieve +6° caster without cutting and welding the tube, (yes I'm cognizant of pinion angle, this is rarely in 4x4 and mile marker hubs are in place) if I use different thickness of steel shims 5° left and 4° right will the leaf springs twist to find a happy medium or will I simply establish torsion, and I should just live with the difference and install two at 4°.
 

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The factory spec for Caster is +.5° to +3.5° with +2° being the preferred setting.  You can go with more, but it will work the steering harder as it will have to lift the weight of the truck to turn.  I'd be looking at the axle housing and make sure it's still straight.  The CAD axles are easily bent.
 

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I believe the spec up through 93, was 3°. At least the 70 s was, and I doubt they changed it.

Those offset bushings, I think are about worthless. For one, you cannot adjust them, and do what the bushing is supposed to do, and preload the ball joints, so that they both share the load.

If you have a difference of 1.2° between the two sides, nothing you do with shims will change that difference.

It amazes me that an alignment shop would let the truck out the door with those specs.

For the record:
  spec (from my 70's book)      Yours
Camber  +1.5°                      +.01°    - .02°           
caster    +3°                        +1°      +2.1°
toe in 1/8" to 1/8" out.      .12 in    .10 in

Do you remember the markings on the offs set bushings?
What tire size are you running?

So where does the wander come from? I think you are thinking right with the caster, but with the difference between the two, I would expect some pull to the right, especially when braking. I think 6° is too much, I would like to see the 3 to 4 range, and closer to the same on both sides. (I suspect the difference is from the offset bushings). Caster is a trade off from going down the road straight, and hard steering. Yes, 2° is noticeable at the steering wheel. I would not shoot for 6°.

The camber?  You have one positive, and one negative, I would like to know what the tech was thinking. Big knobby off road type tires will notice the difference more then tall skinny highway tires. cannot say much without knowing more. But I would like to see them both on the positive side.

Toe in? Thats funny, on any straight axle, with one tie rod, you can only set one toe in, no way to make each side different. So adding the two together, you have .22" toe in. On part time 4x4 systems, Like to see toe in, closer to the 1/8", as the tires will try to pull outwards as you go down the highway. With everything else off, I think the roughly 1/4" inward helps compound the other issues.

Where to go from here? I would try to get the toe in between the 1/8" in, and zero. You can easily do it your self. Measure to the same point on each side (I like to measure from the outside of each grease joint on the tie rod ends), The loosen the bolts on the adjusting sleeves, and turn the tie rod 1/4 turn at a time, and measure again.
You want to shoot for 1/8" further apart. Check that everything is tight, then take it for a test drive. If that is not good enough, I would get 1.5° to 2° shims (steel, not aluminum), and install them to get the caster better.

If still bad, I would get rid of the offset bushings, and start over.
 

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The specs I listed are from my '84 FSM and I am reasonably sure are the same in my '88 FSM but it's out in the truck, it's hot and I'm lazy.  ;D
 

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Discussion Starter · #5 ·
I didn't see the markings on the bushings, but the tech used them to adjust the left hand caster from .8 to 1 an the camber from -.02 to .1.
The right side went from 2.1 to 2.1 caster and .1 to -.1 camber.
I ordered 4° wedges and am hoping I can use the upper bushings to work the difference closer, I put the entire preload at 40 ft/lbs and then tightened to achieve relative angles, I assume a few extra pounds won't hurt the ball joint.
 

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do your self a favor , study how the upper and lower ball joints on a d44 are set so they both share load . Then decide what happens when you turn an off set bushing in the upper for the caster adjustment . (poof there goes your shared load .)  wheel bearings , ball joint preload , loose steering coupler ( even a tiny bit loose )  toe in / out ( you may want to try a few amounts of "in" ).  if even 1 ( one ) spindle is hard to turn because of the sleeve adjustment on the upper , you Will have a wander feel , because of the drag ..... most shops are bad at this , some have the gift of B/S and owners believe them 100%
 

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Elwenil said:
The specs I listed are from my '84 FSM and I am reasonably sure are the same in my '88 FSM but it's out in the truck, it's hot and I'm lazy. ;D
I did not mean to contradict you. I took awhile writing the post, and then saw that you posted in the mean time, and what I had was in line with yours, so I did not go back and change it. Does not surprise me that mopar would go to a broad spec, saves them lots of warranty work fixing their mess up. Took about 6 tries and 2 dealers. to get my 81D150, to drive decent. Found a front end guy that knew more then just setting to spec.
 

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Reviewing the specs the OP posted,  the camber split is negligible and shouldn't have any effect,  the caster split should cause a pull to the left,  toe if in degrees is ok, if in inches its excessive. It will cause tire wear but shouldn't cause driving problems. More caster would be nice,  2 degree shims is where I'd go and try to lessen the split.  Different shims side to side won't fix it.

That said,  it seems to me that something else is wrong.  Perhaps the new ball joints or tie rods are binding,  I've run into cheap ones that are way too tight brand new. I'm willing to bet money that someone monkeyed with the lash adjustment on the steering box and it's now too tight. Hopefully not damaged.

There's a procedure for setting the lash but most aren't aware of it and just crank the screw.  Rather than typing a bunch about that,  I'd try this,  loosen the lash adjustment a quarter turn and see what happens when driving. 
 

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While you're under there,scratching your head, take a good look at the rear springs and u-bolts. Sometimes a problem in the rear will feel like it's in the front. Doesn't cost anything to look.
 

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You can have a horribly pooched steering box, but sufficient caster and properly set toe will still make the truck track straight at speed.

I like to shoot for ~5° caster on a solid-axle rig. There's nothing 'heavy' on the front end of a stock RC that makes the extra caster a problem. The same steering box is used on a cummins truck.

Moreover, is the shop checking the caster will full weight on the truck or not? Caster angle is typically lost as the front leafs springs sag with age; rotating the pinion slightly upward.
 
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