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post #1 of (permalink) Old 05-30-2002, 06:39 AM
Dean
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Setting caster

I'm going to have a new high pinion front end built for my CJ-7 and the builder wants to know where I want the caster set to compensate for lift. I'm going SOA with Alcan 1" lift springs, and I have a standard rotation diff now so I have no idea of what the caster should be set to for this set-up. Is there a way for me to do this when I don't have the springs or front end yet? I hate the idea that I might have to use steel degree shims on a brand new diff.

Dean
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post #2 of (permalink) Old 05-30-2002, 07:17 AM
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Re: Setting caster

If you're going to use a cardan-joint driveshaft, the pinion should be at the same angle as the transfer case output shaft. You can measure that now, assuming you're not going to raise one end more than the other. Then the angle to be built into the yokes is the difference between the output shaft angle and the working caster you want when it's finished.

Typically the front output shaft points up slightly, so theoretically the pinion shaft should point down at the same angle. A lot of guys don't want to do that for clearaqnce reasons. You can tolerate some difference in the angles before the resulting cyclic vibrations get objectionable. Unfortunately I can't give you a an angle at which that happens. If you only lock hubs in on the trail, it's not too significant anyway, but you don't want a real big difference in angles.

If you're going to use a CV joint on the case, you want the pinion pointing at the CV joint. That will be a little more difficult to figure. You'll be raising it about 4". You'll just have to measure and estimate what the pinion angle will need to be.


You can then have the axel built, but leave the spring pads unwelded until you can set it on the springs under the Jeep. Rotate the axel until you have the pinion angle you want, and weld the pads in place.
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post #3 of (permalink) Old 05-30-2002, 01:03 PM
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Re: Setting caster

If he is building a front end, and the yokes are not attached, I would go for somewhere around 7degrees positive caster. You can go a little less, but you will be getting to a point where it will become more difficult to keep it going in a straight line. Caster and pinion angles really are separate issues. If the axle already has the yokes welded in place, then you will have to decide with your builder what the best compromise will be between poor steering and driveshaft vibration. Without the springs I would leave the spring pads loose until you have the springs (if you don't have a built in perch on the diff). You should be able to determine your pinion angle, since it is determined by the position of your t-case. I would set the caster relative to your pinion angle and if possible weld the spring pads after you have the springs.
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post #4 of (permalink) Old 05-30-2002, 03:56 PM
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Re: Setting caster

for caster angle.. it must work with the pinion angle.. which you can not figure out at this time.. but a good caster angle is 6-8 degrees.. and as long as that angle is positive.. then you will steer ok.. even 0 degrees you can still steer... but your return to center (after you turn).. will be less.. meaning you would have to correct the wheel back to straight yourself (this is what your caster angle does).. i am currently running 2 degrees caster.. and its fine..
is this guy local to you? if so.. then you might want to tell him to hold off on welding the ears on.. till you get the lift.. then you can put the axle under the jeep.. put weight on it.. and set your pinion angle and caster angle.. remove axle.. and weld it up..
that would be the best way to do this..
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post #5 of (permalink) Old 05-31-2002, 05:09 AM
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Re: Setting caster

Thanks folks, I'm having the axle built long distance, so the inner knuckles will already be installed. I'll be installing the spring pads once it gets here and I will be running a CV shaft in the front. I guess I'll have to figure out the best compromise once the axle gets here.
Jeepgod - I see that you're running 2 degrees of positive caster. My axle builder said that he normally sets the caster to 2 deg. as well. I've always been told that 5 deg. is optimal for a CJ-7, so I thought that 2 deg. sounded a little shallow to me. You know more about this stuff than I do. Do you have any handling issues using your Jeep on the road? Also, does axle type play any part in what caster should be used on it? I'm switching from a D44 to a high pinion D60, SOA and shackle reversal. When I first installed my shackle reversal, I ended up with a shallow positive caster and at certain speeds the Jeep would sometimes start handling like a shopping cart with wobbly wheels. Once I shimmed the caster back to 5 deg., I've had no problems with it.

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post #6 of (permalink) Old 05-31-2002, 03:08 PM
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Re: Setting caster

actually.. for caster.. it goes by tire size.. the larger the tire.. the more caster you want.. 38" tires.. 8 degrees would be optimum.. like i said.. positive caster is the key..
my jeep handles great on road.. ive done several 12+ hour road trips.. and ive hit speeds of around 85.. with no problems on 35" tires..
i cant explain stopping wobble with just degree shims.. since caster affects your return to center... the tires straightening themselves out after the apex of the turn.. i would want to run 6-8 degrees of caster.. if you find someone with a similiar setup... you can get their pinion angle.. have your caster set at like 7... that way you have some play to rotate it either way..
i used 2 since a wagoneer axles has 6 degrees stock.. so i found a good compromise between it and my pinion angle... i have 12 degrees on my pinion.. which left me with 2 on the caster.. works fine..
if your front end is shaking.. then its usually something else.. rotating that axle might have adversly affected your tie rod ends or something... not sure.. from here..
someone on here must be running the same setup....
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