You are 100% correct on this. At EJS in Moab I talked to Currie and Dynatrac about this. They weld up the knuckles on thier stock JK axles so that you'll have 5 degrees caster and a proper pinion angle for a CV shaft. I forget what lift the presumed when doing this. I'm thinking it was about 4.5". They also said they could make it whatever you wanted on a custom basis.

The shame is that if Jeep had stayed with a real driveshaft and set up the caster ad pinion angle properly for that it would have been a lot better for the average lifted JK.

 

Nope, a lift will decrease your caster and make your pinion angle worse.

 

As you lift the Jeep then the top of the diff will rotate forward...which DECREASES caster. "Caster is the fore or aft slope of the steering axis. The steering axis is a line drawn through the upper and lower ball joints of the knuckle. Positive caster is when the bottom of the steering axis line is in front of the tire's contact patch. Zero caster is when the steering axis is at 0 degrees. Factory alignment specs for basically all vehicles call for a certain degree of positive caster. This ensures good stability, helps maintain straight-ahead direction and promotes steering wheel self-centering." The stock JK has NO provisions for caster angle realignment. Also to consider: "As the JK is raised, track bar angle increases and when lift height exceeds 2" bar length becomes an issue. Bar bind causes the chassis and axle to continuously "tug" against each other resulting in uneven ride height (side-to-side), chassis / frame misalignment and "roll and yaw". Front correction is accomplished via a new adjustable track bar. This route is preferred, as opposed to using a relocation bracket, since the bar's arc-of-travel must remain in-sync with the drag link's arc-of-travel or steering wheel "kick" will result." If you raise your Jeep even three inches, the axle will have shifted and will need to be shifted back over towards the passenger side by about 3/8″ in order to re-center it. The steering wheel also need sto be re-centered so as to not trick the system into activating the ESP/BAS.

Factory caster is around 4.2 (positive), and many folks see, to prefer even a little more with bigger tires (6ish). "As you move to larger and larger tire sizes you alter the caster due to the larger tire footprint. Large tires give you more positive caster. To compensate, you need a new caster setting to offset the larger tires. The following are just suggested starting points. Tire diameters will depend on air pressure and actual specs for the brand and model of tire.
37 in: 5 degrees
35 in: 5.5 degrees
33 in: 6 degrees
<33 in: Adjust to factory specs

Too low of a caster angle will generally result in your steering wheel not returning to center after you complete a turn. The short story is that if you do not cut the knuckles and align your pinion angle (which is MORE important than the caster in terms of vibration from the driveline and the possibility for catatrophic u-joint failure) after a lift, you may use adjustable arms to get the caster the way it was intended...BUT at 6 degrees the pinion is even more downward than it was at 4.2 (factory). If you run it like that, it will steer great (if you also recentered the wheel and relocated/adjusted the track bar to center), BUT count on vibration from your shaft and/or a greatly reduced u-joint life. If you do get it cut and rewelded by a shop that does this for a living, you get the best of both worlds...a lifted Jeep that not only handles like it was designed too but also that is dependable on the trail (and vibration free).

If you don't, you will spend zillions of hours on this and other forums trying to make sense of what everyone else did and what they settled for...but unless they did it the right way, there is no way to beat the geometry equations!

1. Increased driveline angles = vibration and u-joint failure
2. Decreased caster = your steering wheel doing its own thing (while your JK wanders all over the place)
3. Increased caster = increased driveline angle (unless you cut the knuckles and relocate them).

 

I took RedneckJeeps' advice and crossed the tires...no more pull to the right. I also purchased the OME shocks (replaced my RE BB shocks) to go with the OME coils and wow, what a difference. The thing rides so much better with the matching suspension components.

Want to sell my RE BB but have to get a few more posts before I can officially start a "For Sale" thread.

Thanks for everyone's help.

 

Just to throw this out there.. would this approach defeat the need for a new front shaft and could it be done for about the same cost as a new shaft?

 

I didn't "suggest" caster decreased with lift, I SAID it, because it does decrease with lift. I think it would help if you went to your local library and found some basic alignment books. It's all nothing more than simple grammar school geometry. It's just that all of the angles have different names and it can get confusing if you don't know the terminology.

 

Imagine that. Glad it worked.