79'ish CJ7 lift/caster

[Lewman2015]

I have been told that installing 4" springs does not change the caster nor
the pinion angle, as long as I use stock shackles and stock axle perch position.

(I am not using shims or TC lowering blocks.)

Do you all agree?

 

[Torxhead]

Boloney! Have you driven your CJ like that? Also, a lot of newbies have been having issues getting back into this site after newly posting and have to start all over again, so good luck with that!

 

[Lewman2015]

I am getting ready to install the 4" springs on the CJ. How does installing lift springs change the caster?

On a different vehicle (Scout with SOA) I had death wobble and bump steer. That was because of drag link angle-not parallel to center link, and of course, due to altered caster (pinion tilted up).

 

[Woolyworm]

Take a pair of scissors closed (stock lift) then open them a bit (lifted) and imagine your axle is attached at the pointed end of the scissors. See how it will in effect rotate the axle counter clockwise if the scissors are in your right hand?


Wooly

 

[PaRenegade]

It all depends on the spring manufacturer and if they leave a flat section at the axle mounting area or keep it curved. But it's best to check the caster no matter what, and adjust with shims if needed. The factory recommended caster is 5-7 deg. pos., at least for the 80's era. And that doesn't mean that you'd have problems right outside of that range but the further from it the more issues you'll have. Shims are usually sold in 2,4,and 6 degrees. And use steel ones not aluminum ones.

As for the rear, again a shim may be needed in order to match the Transfer Case angle. For instance, if the Transfer Case yoke is pointing down 5 degrees then the pinion yoke should be pointing up 5 degrees (or real close to it). The front pinions angle, in relation to the Transfer Case , takes a backseat to caster angle since the front shaft typically is turning slower when in 4wd and vibration isn't an issue.

 

[LewCJ]

This is Lewman2015-I had to re-register as LewCJ because my PW didn't work.

Thanks guys-Wooly set me straight with the geometry lesson. Since the spring pivots at the back mount, the position of the axle is actually counter-clocked a few degrees along an arc, throwing the caster off. This is because the axle perch/spring mounting surface is not lowered parallel to the frame; it actually "rocks" forward and the pinion tips up. Thus, I need to use shims like the lift manufacturer and God intended. Right???