I want to replace my control arms. I am running a 4" lift and don't have the cash to replace all of them. Which should I do first? upper or lower? Should I just wait till I can do all of them. Stock ones have 12,500 miles

 

You might want to go with lowers first so you can get the proper caster set for the front axle...just a thought, I have Ironman4x4fab lowers and they are freakin awesome and brand new they are only $195. You can get them off his website, just for your info...hope I helped.

 

lowers.. front more important than any other..

 

when you set your caster with new lower arms in the front will that cause your stock driveshaft to fail or can you still run the stock driveshaft

 

Front uppers are the correct choice for adjusting caster (edited, mistake).
The lowers are easier to change so that's what most people do, but the right way is to change the uppers.
Take a look at the forward bolt on the passenger side upper arm. There's not enough clearance to pull it out so you have to loosen it what you can and then cut it off with a sawzall...takes about 10 min. tops...not a big deal.
Plus the uppers are cheaper.
And, as far as your driveshaft is concerned...don't get carried away with too much caster and you will lessen the likelyhood of problems. You can get away with a bit lees than the factory caster spec when running larger tires.

 

The front upper CA's can certainly be used to adjust Caster angle, but they are not necessarily "the correct" choice.

The lower arms provide a wider adjustment range than the uppers, which is one of the reasons they are a popular choice.

In the end if you have an aftermarket driveshaft with double cardan CV joints, the pinion angle will limit the amount of Caster you can dial in.

Ironically, the stock shaft design is actually a bit more tolerant of the pinion angle, though not of total driveshaft angle.

 

Front upper do not adjust for camber, they adjust caster. Also front lowers allow for more adjustment of caster than most aftermarket uppers.

 

TerraFlex's web site recomends front lowers and rear uppers. The guy at the dealer who installed mine did it that way and it drives like a dream!

 

Front uppers are the correct way. Lowers push the front wheels forward increasing the wheel base and misaligning the springs and bump stops(admittedly a small amount), while uppers simply rotate the alxe.
You have to lengthen the lowers quite a bit more to accomplish the same amount of adjustment (caster angle adjustment) compared to shortening the uppers.
The same thing applies in the rear...uppers to adjust pinion angle.

 

The correct way would be to have adj uppers and lowers. But most people get by with adj front lowers and rear uppers. Still, all in all, most of the front uppers out right now don't allow for desired caster unless you add the lowers.