The JKs come with a constant velocity type drive shaft that’s very forgiving to pinion angle variables and they run very smooth but not as rugged as the conventional U-Joint style drive shafts sold by aftermarket companies like Tom Woods or JE-Reel. Another downside to the factory CV shaft is that when you break one you’re not going to fix it on the trail and they are very expensive so more than likely you'll want to replace it with a U-Joint style shaft anyway.

I also run the TF 2-1/2" spring kit on my 08 unlimited and when I changed from a 35x10.50 17 IROC tire to a BFG AT tire with a wider foot print I noticed a little wheel shimmy feed back to the steering wheel around 45mph. The alignment machine says I need to adjust my caster. To correct the castor I need to lengthen the front lower control arms which also pushes the axle forward slightly as it rotates the axle assembly. I plan on installing the adjustable lower control arms to take care of the front wheel shimmy. On the rear the upper control arms are the best solution as wayoflife said especially if you have to convert your driveshaft to a U-Joint style. Another reason for doing the upper arms is that in addition to correcting the pinion angle in a direction more suitable for a future shaft conversion it will center your rear axle more allowing better tire clearance (my 35x15.50 tires rubbed the weld seam lightly on compression like wayoflife warned). Because I don’t tend to drive this JK real hard I am leaving the rear arms stock as well as the drive shafts.

 

Thanks to WOL and Mssbbmia for the mini control arm clinic!!!

 

Great info....Question for WOL or other forum members...If the adjustable front lowers are used to help in tuning the caster, when adjusting the arms are they suppose to be lengthened or shortened & can they be adjusted safely with the Jeeps full weight on the ground or does it have to be raised & supported on jack stands....Please advise, Thank you....

 

you will need to lengthen the lower control arms over stock in order to add more positive caster. this can be done with your jeep on the ground but you will need a floor jack to help things along. also, you definitely need a big ass crescent wrench and a 21mm socket and a torque wrench capable of turning up to 125 ft. lbs.

 

Sorry, I found the answer thru Mssbbmia's earlier post....As for the second question, can the control arms be adjusted with the vehicle on the ground or does it have to be raised...Thank you..

 

LOL...I type as fast as a turtle...Thanks WOL

 

Sorry to jump in here an hi-jack the thread but, I was told when I bought my OME kit to also get adjustable front upper control arms to dial in the caster. It sounds like from the responses here that lowers are preferred for adjusting the caster.

Will it be possible for me to correctly adjust the caster with just the front uppers? Or do I need to exchange them for the lowers?

(2 door Rubicon)

 

My 2 door JK is in a dealers shop now awaiting aftermarket driveshafts. Is there anything special that will need to be done to my 3" FT Ultimate lift after installing? Worried that the shop may not know what to do. My rear driveshaft went out after only 4,000 miles. Thanks.

 

technically, uppers ARE what you want in order to adjust caster. the only problem is, most of the aftermarket adjustable upper control arms available today cannot be adjusted short enough to give you what you want. however, being that adjustable lower control arms will need to be lengthend to give more positive caster, this works out just fine and essentially does what cam bolts would do and without having to notch out your mounting holes.

hopefully they know that your rear pinion angle will need to be set so that it's in line with your rear drive shaft. also, up front, if you have 5.13 gears, you may need to have your caster kept at or returned back to a stock +4.2° as any more than than and you may experience vibrations. this is not a rule, just something i have seen guys have to do including myself.

 

Ok, it's my turn to hijack the thread. (just kidding) Alright, I put my 2.5 spring kit from Teraflex on and frt. and rear adjustable track bars with 35's. I finally took it to the alignment shop today to get the Toe adjusted. I asked for the print out of the alignment and it says my Camber is -0.4 lft frt, -0.4 rt frt (both before and after) the Caster is 2.4 lft frt, 2.4 rt frt (both before and after) and the toe was off a little 0.08 lft frt 0.24 rt frt (before) and 0.10 lft frt 0.11 rt frt (after). I asked the guy about how bad I needed control arms, sooner/later, what? He said that the caster was really only a little low and since they were equal, it should be fine. Honestly, the Jeep drives pretty good. How much better should I expect it to get if I decide to get the control arms? I mean, do I really need em'? Some of you technical guys give me some feedback.