resharp001

Well, you're not the only one. You'd be surprised how many people it hasn't really "clicked" for. I remember being in that boat long ago too.....so I get how it's confusing even though it really is a simple concept. I will always push for someone to take the time to understand it rather than just take it to someone and as them to make it right. Tiny bit of knowledge can go a long way.

nthinuf

It's amazing how many people talk themselves into thinking it's fine the way it is, and can't be bothered to spend a few minutes trying to understand the issues involved with lifting.

I actually laughed over this:
since the Note attached right to the bottom of the 3" lift on their website tells people to add adjustable arms so they can correct the caster/pinion. Like, hey folks, caster adjustment is not included with this lift. Hint hint, think about this...

MikeOK

Okay I am still confused by one thing. If I understand right I want to shoot for 1-2* pinion angle, and that means the back is 1-2* lower than the front, right? So if I have a pinion of say 0* then my caster is 6* and need to lower the rear a bit by lengthening the CA? Wouldn’t that put more stress on your DS by increasing it’s angle at the axle? Or by lifting it I will end up with a lower caster rather than higher?

Edit-Never mind, I found my answer. Raising it increases pinion angle and decreases caster.

resharp001

Your pinion coming out the back of the diff right now is pointed too far up....which is decreasing the angles that your C's are at. you want to lower that pinion a bit. I'd shoot for a pinion angle of 1.5* - 2*.....which would put your caster in the 4* - 4.5* range. As you lengthen the lower arms as you're going to do....you're pushing the lower axle mounts forward....which is going to lower the pinion. When you go to install those arms.....if you put a floor jack right under the diff and slowly raise it, that will help rotate the axle to get the bolt hole in the bracket to line up with your arm. Conversely, if you'd put the jack under the pinion flange itself to shorten up that distance.

Note....you could get some wide ranges of measurements depending on where you put angle finder. Just make note of what you measure, and then you'll have a basis to go from a computer alignment as well. For example...if you measure pinion angle at 2*, that would mean your caster is 4*. Well, if you go to the alignment shop and they actually read that your caster is 3*.......and you are targeting 4*, then you know you simply have to adjust until your angle finder measurement from the exact same spot you measured before drops by 1*. I'm probably just confusing things more.

kjeeper10

TF is not entirely correct. Need ? No but will benefit most lifted JK's.

Read my post earlier as far as measuring first. I put the angle/phone right on the flat of the pinion flange.

Stock should be around 2° pointed up. Lifting brings it up which lowers caster. Longer lower arms brings it back down.

Get a reading and then go in for alignment. Whether you do it yourself or not its good to get the baseline.
In my case i set my pinion to 2° (should equal about 4° caster) but when on rack showed 3°
Later after arriving home I shortened my uppers to drop the pinion 1° (actually read 1°)

Setting toe is the same for me. Im always + 1/8-3/16 on the rack compared to home w/ tape measure. So now i set toe 0 between front and rear. Last check i was right at 1/8 in.

Its not hard to do any of this. Many video's on YouTube to help. Regardless its still good to have the alignment checked to compare #'s or get a baseline for future changes.

resharp001

I would note also......these aren't going to be dramatic changes to the naked eye. I mean, we're talking 1 - 2* of angle. BUT.....those little degrees make a pretty big difference when it comes to caster. So it's not like you're going to look under the jeep and go "oh man, my pinion is pointing WAYYYY too high". These are gradual adjustments that make a significant difference.

MikeOK

kjeeper- Im reading the long alignment thread over on wranglerforum, I assume that’s you? Thanks for helping us greenies out.

Again, I have to ask, if you have a pinion angle of +2* does that mean the rear of the diff is lower than the front by 2*? Simple question I know but I haven’t read anything yet that clears this up.

nthinuf

Look at the diagram in post #27. It shows the pinion at 0*. (parallel to the ground). If you rotate the entire housing so that the pinion is now 2* higher, then yes, an imaginary pinion on the front of the housing would be angled 2* lower.

The point to keep in mind about this is that caster and pinion are inter-related. Raise one and the other lowers. With a lift and high caster (better steering), you start getting vibes in the front driveshaft. With a lift and low caster, the steering is crap, but driveline angles are better. So you have to balance the two.

MikeOK

So I was incorrect, going from 0* to +2* would raise the pinion. (I think, changing to daylight savings time confuses me too)

nthinuf

Yep. It can be really confusing when first thinking about at it.

But on that diagram, it's easy to see the correlation. By raising the pinion 2*, the horizontal black line indicating the pinion axis is raised 2* on the right, and lowered 2* on the left. At the same time, the vertical black line indicating caster rotates counterclockwise an equal amount, reducing caster from 6* to 4*.

High caster gives better steering. But, it has the pinion pointing further down, which gives steeper angles on the driveshaft joints.

Pinion pointed higher gives better angles on driveshaft joints, and can get rid of vibes. At the expense of lower caster and worse steering.