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Discussion Starter · #1 ·
I've searched here but no luck...

I got the spring pads off and as soon as my welder comes in I wanna get the axle back under the truck to start mocking up the steering... Im lost at the moment any help would be pure awesome :)

From googleing it a learning alot about caster, the trooper was (guessing) 5-8 degress positive and every pot hole was hell.. Cause the tire would tuck in so, Im almost there I no it has to be set neg. But not sure how far..

Im not sure if its differnt for tire sizes? But im runnin 15x12/35's
Thanks in advance guys :)
 

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Caster is a line drawn top to bottom through the ball joints. Think fork rake on a motor cycle or bicycle. This affects self centering of the steering wheel mainly. If you are doing a SAS then yes it's critcal. It is set by where you weld on the spring plates. Changed by rotateing the axle tube. You have to be careful as this also affect the pinion angle as well. This is why On highly lifted trucks the knockles often need to be rotaded on the axle tubes once the pinion angle is set. That's not a job for the backyard guy. Camber is often fixed on a solid axle. You want that caster either set to pretty close to factory for the truck or the truck the axle came out of with the weight on the springs.
 

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Discussion Starter · #4 ·
Im not confusing caster with camber, im highly aware of camber and i hated it on my honda due to replacing tires (but u gotta pay to play(or buy a camber kit)) anyway close to stock i can do cause the stock spring pads are there (on the bottom) but the trooper was already sas'd and the top balljoint was farther forward then the lower wicth was making the tires fold in on the slightest turn at any rolling speed..
For a example here if u guys are still not understanding what im refering to, use ur hands say 3 inches apart pretend that ur thumb is the upper ball joint and ur pinky is the lower.... Now turn.... That is a bad setup IMO, but anyway...

The pinon angle is waaay up there and its got to be lowered anyway.. (cause im pushing the axle a few inches forward)

but my main consern was making a turn and the steering wheel NOT coming back to center meaning caster angle is waay off....
 

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Yes the top ball joint should be behind the bottom. I can't imagine driving a vehicle with negative caster! No wonder that thing was scary to drive. The pinion shaft should be parallel to the ground. The spring plate should be close to that as well. If it's too far off then the spring mounting to the frame probably needs tweaked as well. I now remember your original post about this front end. OMG!

My factory manual calls for 2 degrees of caster for a 1st gen Trooper. That's for IFS. it may or may not be ideal for a straight axle.

If it was me in your situation. I would probably set the axle on jack stands or blacks held securely in the proper position. With the truck above it centered where you want the axle in relation to the frame and body. Remember the axle will move to the rear when the spring is compressed. Then I'd set the spring mounts on both the axle and the frame to align the spring to fit the space between.
 

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It also depends on what axle your using. A D44 would be good set around 4-5 deg. I put a Toyota axle into my 91 amigo and set it at 6 -6 1/2 deg. To much or to little can make for wobble/wandering and not centering. It sounds like you has tons of positive caster top ball joint infront of the bottom one. I've got some pics on my blood sweat and tears post or the flex test one take a look and see if it helps. After I put my axle in my oo amigo I had to cut the welds on the bottom link arms and reset the caster it handled bad.
 

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Discussion Starter · #7 ·
Yeah it was horrable.. Soon as the new pads and welder get here i can mock it up and see how far 4 degrees is going to move the pinon angle..
 

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Discussion Starter · #8 ·
Yeah it was horrable.. Soon as the new pads and welder get here i can mock it up and see how far 4 degrees is going to move the pinon angle..
 

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You want positive caster. For a solid axle somewhere between 4 and 6 degrees. Just a refresher for people reading this thread.


Most axles you buy out of a used truck will sit the pinion level and give the correct caster. Also keep in mind the bottom of the cast housing is not always parallel to the pinion shaft. Use an angle finder on the yolk and set it at 0*/90*. Some stock trucks came with up to 8 degrees of caster so it all depends on what axle you bought.
 

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They also check that when the wheel is turned to much will make the tire tip out on sharp turns and it eats up tires. I had les Schwab check mine after I adjusted the bottom link arms and it was in specs,I think I had them base it off the jeep. They where slightly confused lol. If you have a tall lift/ride height you might want to turn the axles to help bring up your pinion angle.
 
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