Hi, on a JK, when you lift the front end significantly, in the range of 5.5-6", using short arms, which way does the differential typically need to be rotated to correct caster angles? Does the pinion tend to rotate down or up as you lift it higher? After I find the answer to that question, my next question is, if you were going to use one set of adjustable control arms to be able to adjust that caster and pinion angle, which would be the best ones to replace with adjustable ones, the uppers or lowers? My JK Unlimited Rubicon has about that much lift, my lift kit came with new fixed length lower arms for front and rear, and I'm running 37's. I want to address what little bit of "wandering" I'm experiencing. To sum up my questions in one sentence, "Which way should I have to rotate my pinion to get the correct caster angle, and should I use upper or lower control arms to do so?"

 

You want frt lowers to correct caster. With that much lift your frt drive shaft, if stock, is at a horrible angle with fixed arms.

 

Thanks. If I use front lowers, do I make them shorter (rotate the pinion up) or longer (pinion down) than stock to get towards the correct caster and pinion angle? I'd think shorter would rotate it up to lessen the angle, correct? If that's the case, wouldn't using uppers and making them slightly longer than stock net the same results, or would that cause other problems? Just wondering, trying to get a grasp on how this works, not saying you're wrong, by any means.

 

Longer. There is a great thread in Planman signature explaing control arms. You will get many different answers, but a caster total of 4.7 to 5 I would think would be good. Now advice from guys running that height would be great to hear from on what they run.

 

you need to make them longer but really, you can only make them so long before you start having other issues like your driver side coil making contact with your sway bar and your passenger side hanging up on the bump stop tower. of course, as mentioned, your pinion angle wouldn't be looking too great either. to do this right, you really should get both adjustable upper and lower arms so that you can push your axle foward back to where it should be and then use the upper arms to set your caster.

 

Ok, you're saying to go longer with lower arms to correct caster angle, but if I'm thinking about it correctly, that would make driveshaft angle WORSE. If I need to lengthen lower arms to correct caster, I guess I could go with a CV driveshaft for that much lift to correct the angle problems with it, couldn't I? I'll try to find his CA write up, also.

 

that is correct, it would be worse IF you only tried setting your caster with lower arms alone. while lower arms can get address caster, their main purpose is to reposition your axle under your jeep. technically, your upper arms should be used to set caster but, they are harder to install. with as much lift as you have, BOTH should be used to do things properly.

 

Oh, ok Wayolife, I see what you're saying, a combo of both upper and lowers sounds like the best choice, for sure. Will the CV driveshafts handle those angles better?

 

when you say "CV", are you referring to rzeppa joints like what come from the factory? if so, no, at your height, the angle the cv boots will sit at will cause them to fail prematurely. you really need to be running a u-joint style double cardan shaft.

 

OK. Not really sure what type I was looking at. I had just seen online where some companies were selling driveshafts that said they eliminate driveline vibrations, etc...but could've sworn they were calling them CV driveshafts. I'll dig into that more, and see exactly what they are.