Clayton front arms

[wwood]

While I would have agreed that 5° of positive caster was a good thing 6 years ago, I would not recommend you do that now. Depending on what gear ratio you are running, this will cause driveline vibrations and over time, will lead to transfer case housing failure. How do I know, it's happened to me and I have personally seen it happen on 2 other JK's. Since then, I would only recommend that you restore your caster back to stock which is about 4°.

Having said that, you cannot just set your lowers and upper arms to fixed lengths and expect your caster to be some exact angle. To suggest that is just stupid. If that were true, you could install any lift you want with stock arms and nothing would change and that's just not the case. The amount of lift you actually have changes the angle you need/want and that's why adjustable control arms are nice to have - so that you can make changes to the angle. If you have both upper and lower adjustable arms, you'll want to use your lower arms to set your axle position and your upper arms to set your caster. I do use 23" as a starting point but, depending on how much lift you actually have, I often find that they need to be set them a bit shorter. With the upper arms disconnected from the axle mounts, use a floor jack to raise or lower your axle angle from the pinion until you have the caster you need. One of the easiest ways to do this is to take an angle finder and place it over the flat spot on the front of your differential where you would normally attach a case spreader as shown below...

[image snipped]

When you have a reading of 0° here, you will have 4° of caster. Set your control upper control arms so that you can get one installed on the axle, measure it's length and then set the opposite side arm according. Getting the second arm installed can be tough and using your floor jack to raise or lower your pinion will help to make this possible.

Thanks Eddie, I really appreciate this info. I am installing a full set of adjustable arms with 3" EVO plush coils this coming week and your tips will save me a lot of guessing.

 

[JKUx]

This is great as I will be getting the upper arms in the future, Eddie thanks for the detailed info.

As for the EVO 3 inch plush ride coils, I absolutely love the ride and the way my JKU sits!

 

[JKUx]

So I went to the ace hardware store for some 90* grease fittings and found this.
That should work for pinion angle when I pick up the UCA right?

 

[wwood]

View attachment 75670
So I went to the ace hardware store for some 90* grease fittings and found this.
That should work for pinion angle when I pick up the UCA right?

Yes, that is the same angle finder Eddie uses in his writeups and the same one I have. Even though its plastic I find it super accurate. Only issue is whether you can find a truly level spot for the Jeep when using it. My garage floor has a built in slope so water will drain out and my driveway is sloped even more so I have to account for the slope in the readings. I put the angle finder on a 6 foot level (a long straight board would be just as good) to measure the garage floor slope (about 1*) and add or subtract that from the readings I get on my Jeep when using the angle finder to set caster/pinion.

 

[JKUx]

Yes, that is the same angle finder Eddie uses in his writeups and the same one I have. Even though its plastic I find it super accurate. Only issue is whether you can find a truly level spot for the Jeep when using it. My garage floor has a built in slope so water will drain out and my driveway is sloped even more so I have to account for the slope in the readings. I put the angle finder on a 6 foot level (a long straight board would be just as good) to measure the garage floor slope (about 1*) and add or subtract that from the readings I get on my Jeep when using the angle finder to set caster/pinion.

Thank you very much for the info.

 

[wwood]

[snip]

One of the easiest ways to do this is to take an angle finder and place it over the flat spot on the front of your differential where you would normally attach a case spreader as shown below...

When you have a reading of 0° here, you will have 4° of caster.

[snip]

Eddie, could you check this again please? I am just now working on my Jeep's caster and I think you meant, "When you have a reading of 0 here, you will have 6* (not 4*) of caster."

This link indicates that with the pinion angle at 0, caster is 6* and I read somewhere that the 2 oval flat spots on the front of the differential are machined at 90* to the pinion center line which I confirmed with the angle finder:

http://project-jk.com/jeep-jk-tech/...o-i-measure-it-and-how-does-it-affect-my-jeep

So in setting my caster to 4* I would want the reading on the flat spot to be 88* or 92* depending on how the angle finder is oriented - correct??? In other words, the pinion should be angled up 2* so caster is automatically set at 4*?

Will appreciate your feedback.

Thanks.

 

[wayoflife]

A ProRock 44 Unlimited comes with 6° of positive caster. Factory is about 4° and when your see 0° at the front of the diff, you should have that on a factory axle.

 

[wwood]

A ProRock 44 Unlimited comes with 6° of positive caster. Factory is about 4° and when your see 0° at the front of the diff, you should have that on a factory axle.

Sorry, I didn't explain my point too well so I will try again.
Here is Dynatrac's description of what I meant copied from the link in my last post:

"As you can see by the drawing, stock caster to pinion angle separation is 6*. This is represented as the pinion at 0* (zero rise) or 90* at the pinion flange face and the caster set at 96*. If we were to rotate the pinion up to stock JK position, the pinion would be tilted up 2* and caster angle now would be 94*. In alignment terms, this is known as 4* of caster. A stock JK has 4* caster and 2* of pinion up tilt for a total of 6* of separation."

So with the pinion angle at 0*, meaning parallel to the ground, zero rise, caster would be 6*. If pinion angle is 0*, we will get a reading of 90* from the Johnson angle finder sitting on the oval flat spots on the front of the differential (as shown in your photo) and therefore caster would be 6*. But we need the pinion to tilt up about 2* so we need to see a reading of 88* or 92* on the angle finder depending on what direction (passenger or driver side) you take the reading from. Then when the pinion is tilted up 2*, we have 4* caster.

So it appears that there is a typo in your post (either that or I am totally wacky ) The reading on the angle finder should be 88* or 92* which means pinion angle is pointed up 2* and caster is positive 4*.

Here are some pics which will hopefully explain what I am trying to say:

First I leveled Jeep with floor jacks under front axle to neutralize the slope in my garage


Angle finder on driver's side flat spot


Angle finder on passenger side flat spot


Angle finder on rear pinion opening


Wider view of angle finder on rear pinion


View of pinion yoke and front driveshaft relationship, angle between the two is not too steep.


Angle finder on passenger side ball joint top, directly reading caster of 4*

 

[wayoflife]

I apologize - you are correct and I was mistaken. Back in the early days of the JK, setting your caster to 6° after installing a lift was common as it helped improved handling and the information I gave was just what I was used to saying. 4° of caster as what you got from the top of the ball joint is what I do recommend now being that time has shown it to do better at preventing drive line vibrations. 92° or 88° as you are showing at the front is correct.

 

[wwood]

Eddie,

Thanks for the help, glad to hear my caster is in the ballpark. Now I can torque all my arms back up and do a test drive.

Some folks may be interested in a follow up on the original issue in this thread about control arm length.....

I am putting in a set of 8 adjustable control arms. I set my front lowers to 23" as per your recommendation and for starters I set the front uppers at 18.75" which is the factory length. But with the front uppers that short my caster was close to 6, so I had to lengthen the front uppers to 19 1/8" to get caster back to 4*. Your recommendation of 23" for the front lowers is excellent, it positions the front axle very well, no clearance or interference issues and the upper bump stop falls nicely centered on the axle spring perch at full stuff.

 

[wayoflife]

Eddie,

Thanks for the help, glad to hear my caster is in the ballpark. Now I can torque all my arms back up and do a test drive.

Some folks may be interested in a follow up on the original issue in this thread about control arm length.....

I am putting in a set of 8 adjustable control arms. I set my front lowers to 23" as per your recommendation and for starters I set the front uppers at 18.75" which is the factory length. But with the front uppers that short my caster was close to 6, so I had to lengthen the front uppers to 19 1/8" to get caster back to 4*. Your recommendation of 23" for the front lowers is excellent, it positions the front axle very well, no clearance or interference issues and the upper bump stop falls nicely centered on the axle spring perch at full stuff.

Glad to hear it. Would you mind if I used your angle finder pics to update my write-up?

 

[wwood]

Glad to hear it. Would you mind if I used your angle finder pics to update my write-up?

No, of course not, it's my pleasure. I can't tell you how much I appreciate and have learned from your posts and write-ups, so it's great to hear the pics might help a little.

 

[wayoflife]

No, of course not, it's my pleasure. I can't tell you how much I appreciate and have learned from your posts and write-ups, so it's great to hear the pics might help a little.

Perfect, thank you

 

[Sugarbear]

So got the arms on today uppers set at 18.75 and lowers at 23 and I can't belive how well it handles now but my question is i started out with 3.5* now I currently have 1* on the angle finder can anyone tell me what that would make the caster?? I see 2* is ideal but is my 1* not right ?

 

[wwood]

So got the arms on today uppers set at 18.75 and lowers at 23 and I can't belive how well it handles now but my question is i started out with 3.5* now I currently have 1* on the angle finder can anyone tell me what that would make the caster?? I see 2* is ideal but is my 1* not right ?

Not sure I understand where you have the angle finder to get a 1* reading. If you have the angle finder on the oval flat spots on the front of the diff your reading should be 88 or 92 depending on how you are looking at the finder. That reading gives you 2* of up pinion angle and 4* of caster.

I just installed adjustable front arms on my 4 door and started with 23 for the lowers and 18.75 for the uppers. Those settings produced almost 6* caster which is too much. The angle finder on the oval flat spots was reading about 90* meaning 6* caster and 0* pinion angle, not good. So I had to increase the length of the front uppers to 19 1/8 to get the caster back to 4*, meaning the angle finder read 88* (or 92*) on the oval flat spots.

Your Jeep might need a different length for the uppers since it is a 2 door, don't know since I never worked on a 2 door.

Pretty sure pinion angle is important on a 2 door since the front drive shaft is so short. Are you running the factory front shaft?

 

[Sugarbear]

Not sure I understand where you have the angle finder to get a 1* reading. If you have the angle finder on the oval flat spots on the front of the diff your reading should be 88 or 92 depending on how you are looking at the finder. That reading gives you 2* of up pinion angle and 4* of caster.

I just installed adjustable front arms on my 4 door and started with 23 for the lowers and 18.75 for the uppers. Those settings produced almost 6* caster which is too much. The angle finder on the oval flat spots was reading about 90* meaning 6* caster and 0* pinion angle, not good. So I had to increase the length of the front uppers to 19 1/8 to get the caster back to 4*, meaning the angle finder read 88* (or 92*) on the oval flat spots.

Your Jeep might need a different length for the uppers since it is a 2 door, don't know since I never worked on a 2 door.

Pretty sure pinion angle is important on a 2 door since the front drive shaft is so short. Are you running the factory front shaft?

It's a coast shaft I'm just gonna get it put on the alignment rack and see where it is exactly then adjust if I have to but right now it drives pretty close to stock so I can't be to far off

 

[wwood]

It's a coast shaft I'm just gonna get it put on the alignment rack and see where it is exactly then adjust if I have to but right now it drives pretty close to stock so I can't be to far off

Ok, let us know what the alignment rack says.

 

[Sugarbear]

Ok, let us know what the alignment rack says.