I have a question. I am running at, or very near 6" lift on my 07 4 Door Rubicon, 6 speed, and am running the stock driveshaft in front (soon to be replaced, due to issues with fat stock shaft contacting the exhaust crossover at full left front droop). I have about 4.5 degrees of caster in my front axle, and it is a little bit "darty", "flighty", or wanders some. I understand to correct that, I need around 6-9 degrees of caster. In order to get that kind of caster, you actually lengthen the lower front arms, and rotate the pinion DOWN. As you do this, you make the driveshaft angle worse. Now, my question is, are most aftermarket front driveshafts the double cardan CV style, like the aftermarket rear shafts are? If so, and it's like the rear, you have to rotate the pinion up, to the same angle as the driveshaft, pointing to the transfer case, or the center of that double cardan joint, in order for that shaft to work properly. If you did this in front, you'd end up with negative caster numbers, wouldn't you? I couldn't imagine it wandering worse than it does now, so...how does this work with new aftermarket front shafts??

 

No, you don't have to rotate the rear if you your putting in a double cardan drive shaft. That type of joint is used for that reason of high angles from the transfer case to the rear. Add more caster to your rear and change out the front drive shaft.

 

Just lengthen the front lower control arms some. I do believe though that most of the front shafts do have the double CV shaft.

 

You will get various responses, but IMO with that much lift you need, if you don't have, frt upper and lower arms. Caster you would want at 4.7 to 5 total. Maybe a bit more. As you push the axle with the lowers, the uppers will allow the pinion to align with the driveshaft. I just did this over the weekend. You definetely want a double cardan shaft, as the factory shaft at that angle is really bad with that much lift.

 

Yes you are correct with that much lift you need to increase caster to approx. 5 degrees, maybe more. Basically as you increase caster your handling will improve and the pinion angle will increase. So it becomes a balance between handling and vibration. Idea is to have as much caster as needed with no vibration, this will vary from Jk to JK. I have 4.5" of lift and I ended up at just a hair under 5 degrees+ caster. No vibration and it handles very well, no more flighty steering.
As for your front drive shaft, you want a double cardan joint at the transfer case end and I believe all aftermarket shafts come this way unless it is a stock replacement.

 

with so much lift, you really need to be running adjustable front upper and lower control arms. you need to use your lower arms to set the position of your axle back where it was under your jeep and then use the uppers to set caster. this will help limit the amount angle you have at the pinion when setting your caster.

you only set the pinion on the rear because - you DO NOT set the front in the same way. to do so would negatively effect caster and that would be a problem. you need to balace the amount of caster you have while trying to minimize the amount of angle you have at the pinion. caster is an important part of front end alignment and you need to keep it at least at about +4°. more will help make your jeep handle better at highway speeds but, you will run the risk of drive line vibrations.

 

Thanks for the replies. The answers I received were pretty much what I thought, I just wanted some feedback, or some verification, I guess. I really think the main reason I'm going to have to change the front driveshaft out, is because of the aftermarket ones being smaller diameter, allowing more clearance between it and the exhaust crossover.