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caster to pinion angle

DeftwillP

DeftwillP

NAXJA Forum User
Location
Round Rock TX
What is the difference between the caster and the pinion angle on a HP d30? Assuming that regular balljoints are used and the knuckles haven't been cut and turned, there should be a fixed and set relationship between the two no matter what height of lift, right?

I've thown a cheap angle finder against the front of my ruffstuff cover and used gojeeps site to come up with the approximate caster. I can't seem to accurately find the pinion angle though. The point of all of this is that I'm wanting to do some offset balljoints so that I can point my pinion higher up and still get a high positive caster (6 to 8 degreees maybe).

Any help in this department?

(please don't respond with use adjustable control arms as you clearly didn't read my question)
 
The OEM spec for the relationship between the front pinion and the front DS is 0 Degrees. Since the location of the inner "C"s are fixed at the Dana factory, this also sets the OEM Caster.

When you lift your Cherokee, you change both the Caster and the Pinion angle because the axle housing rotates as it drops.

Most people who lift their Cherokee and don't want to cut off the inner "C"s and weld them back on make lemonaid and split the difference between ideal caster and ideal pinion angle, which results in the pinion being a few degrees low in relation to the DS. Some people use adjustable upper ball joints to tray and make better lemonaid, but it is still lemonaid.

BTW: Caster is measured at the "C", not the axle housing.

hasta
 
Last edited:
WB9YZU said:
BTW: Caster is measured at the "C", not the axle housing.
Click to expand...


I know. I don't have the outer "C" and balljoints out at the moment. That's why I mentioned the gojeep method as it's supposedly tried and true. For some reason though, he doesn't list the pinion angle with his chart.
 
whitexj98 said:
While reading thru the TNT long arm kit instalation (will be installing when it arrives) they mention that diff cover angle minus 9 equalls caster...if that helps.
Click to expand...


Yup, gojeep's chart shows the same. But what is the pinion angle then in relation to say....5 degrees caster?
 
Wow thats a tough one,wait....9-5=4
 
RCP Phx said:
Wow thats a tough one,wait....9-5=4
Click to expand...


Que? I see how this gives us the caster. There is a relationship between the angle on the side mounting boints of the diff cover and actual caster but what is pinion angle? Basically, without changing balljoints or doing a cut/turn, you should be able to take one measurement and then know both the caster and pinion, right?:anon:
 
You also have to factor in the lift height altering the drive shaft/pinion angle. I have read that the stock difference between caster and pinion angle is 6 degrees.

As mentioned, pinion angle is slightly more important than caster, and most people just compromise. I have never measured caster or pinion angles as I progressed from 2" -> 3.5" -> 5.5" of lift. At 5.5" I set the pinion angle by eye and adjusted it slightly for better caster after the first test drive.
 
Last edited:
DeftwillP said:
Que? I see how this gives us the caster. There is a relationship between the angle on the side mounting boints of the diff cover and actual caster but what is pinion angle? Basically, without changing balljoints or doing a cut/turn, you should be able to take one measurement and then know both the caster and pinion, right?:anon:
Click to expand...

4* is the pinion angle.
 
Pinion Angle > Caster! I always adjust mine just enough to eliminate driveline vibrations and leave it. Always end up with more caster than stock but its lifted and that happens. The only way to eliminate it is to cut off the C's and reweld them.
 
sheffeyva said:
Pinion Angle > Caster!
Click to expand...

strongly disagree. ill take safety and drivability over vibrations.t and at what height do you start getting vibes from it where you need to adjust the pinion angle? ive run between 3 and 5.5 on a dana 30 always with acceptable caster and never a vibration.
 
ktm racer 419 said:
strongly disagree. ill take safety and drivability over vibrations.t and at what height do you start getting vibes from it where you need to adjust the pinion angle? ive run between 3 and 5.5 on a dana 30 always with acceptable caster and never a vibration.
Click to expand...
I'm at about 5" of lift. I don't run crazy caster angles if thats what your referring to but I was not able to maintain stock. I was getting vibes at low speeds from my front shaft for some reason. Adjusted the pinion up slightly and it solved my problem. Never had issues on the highway driving it but it's not my DD and mostly just hits trails nearby.
 
Last edited:
ktm racer 419 said:
strongly disagree. ill take safety and drivability over vibrations.
Click to expand...
x2 handling appropriately and safety come first. Unless you run 4x4 on the road you won't really notice it. My alignment is biased to correct caster and I get a bit of vibes on 4x4 full time but nothing to complain about. But I'm only at 3.5"
 
ill measure it tomorrow. when measuring your pinion angle though, use the yoke. turn it where one ujoint saddleis above the other, and set your angle finder across it. I dont trust the diff cover surface.
 
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