Caster Question

I know that having too much negative caster can cause wandering and a bad return to center of the steering wheel. Can these symptoms be the same for having too much positive caster? I have a waggy D44 that I built up and am having these problems. I have not turned the inner c's, but I have the coil buckets welded on so that the pinion was pointed up towards the t-case a bit. At ride height my pinion angle is a bit low, but I didn't see it as a problem because I wanted to try to get a better caster angle and I have locking hubs. Any help would be great. I wish I had the degrees that the pinion is pointing up at, but I don't have my angle finder with me right now. Here are a few pics. I hope they help somewhat. Thanks for the help.




-Matt

Looking at just the pinion, it definitely could use some more caster. Lengthen the lowers some.

Wouldn't I want to lengthen the upper so the pinion would tilt up? Lengthening the lowers looks to me like it would lower the pinion.

XJ_Jeeper01 said:

Wouldn't I want to lengthen the upper so the pinion would tilt up? Lengthening the lowers looks to me like it would lower the pinion.

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Castor angle is more important than pinion angle. The inner C's should have been rotated. Set it for about 4.5-5 degrees of castor angle. This will correct drivabilty issues. If you want to correct driveline vibration start over with the inner C's rotated to the proper angles for both caster and for the pinion angles. The only other choice would be a 2 piece driveshaft with a center bearing. Use a CV joint at the T-case and angle it down to match the amount the pinion angles up, this is where the center bearing will go. Then use a standard 2 joint shaft with a slip yoke from the center bearing to the diff.. That won't be cheap and isn't the best fix. Otherwise just set your castor corrrectly and only lock the hubs and use 4wd at low speeds.

IMO, I would rotate the inner C's and set the axle up correctly.

So far there has not been any driveline vibrations. I figured that the only way to really fix it would be to turn the inner c's. But I'm still curious as to if you will have wandering with too much positive caster. Thanks.
-Matt

4.5 to 6 degrees of positive castor should work fine. The pinion angle should be about 1 degree less then the driveshaft angle. Yours looks to be about 4 to 5 degrees more the the driveshaft angle, I'm pretty sure you have driveline vibs at 50 to 60 mph with the hubs locked in right now.

Unless I'm misunderstanding you, you tilted your pinion up, to align your front drive shaft. That results in reducing your positive caster--not increasing it. Positive caster is the tilting of the ball-joint axis to the rear. By leaving the upper CA's alone, and lengthening the lower CA's, you will move caster in a positive direction.

TNT said:

4.5 to 6 degrees of positive castor should work fine. The pinion angle should be about 1 degree less then the driveshaft angle. Yours looks to be about 4 to 5 degrees more the the driveshaft angle, I'm pretty sure you have driveline vibs at 50 to 60 mph with the hubs locked in right now.

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Which is why I leave the hubs unlocked, and what I meant was at low speeds(in 4wd) I don't have vibes. Sorry I should have clarified that. So 4.5-6 degrees. Thanks for the info. Looks like I'll be turning those inner c's sometime soon.
-Matt

Did you ever think about adjustable ball joints?

negative caster gives the "shopping cart" steering where it's squirrely, easy to turn, but doesn't want to return to center. positive (too much) caster will make it harder to turn, wants to stay on center. as bubba pointed out, you introduced negative caster when you pointed the pinion upward. on my scout i had shims under the front leaf springs to point the pinion downward to get more positive caster, but if i left the hubs locked in over winter it ate front driveshafts.

outlander said:

Did you ever think about adjustable ball joints?

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I have, but those ball joints are brand new and I didn't want to spend more money on something that I already have(I know they are aren't adjustable), when there is a fix for it that's free.

Rotate the C's... you'll be much happier in the end. I've had two Waggy 44s under XJs and without rotating the C's I don't like the handling at all. Spend the change to do it right.

Later,
Joe

Yea I'll be rotating them next weekend when I have some extra time. Thanks again everyone for the replies.
-Matt