Here's the history of my steering box brace. I lifted my Jeep and mounted 33 inch tires in June of 2000 with 96,000 miles on the clock. A couple of months after the lift I added Rusty's steering box brace to strengthen up what I thought was a weak point.
A couple of weeks ago (137k miles) I added a Hansen bumper and a Warn winch to it. Last weekend I took a long trip to the Arizona Strip which included about 350 miles of high speed dirt road driving. I got off the dirt onto the highway and noticed that my steering wheel was off center. I crawled underneath to have a look around and noticed a crack on the bottom of the frame rail right underneath the steering box that ran between the sway bar mounting bolts. Here's a look at the crack:
I checked the steering box mounting bolts- they were all tight, just as they have always been every other time I checked them. Closer inspection showed that the two layers of sheetmetal that formed the frame rail have buckled and split apart.
What I have surmised from looking at the damage and my recent mods and use: The steering box brace caused the driver's side frame rail to flex in a lateral direction whenever the unibody flexed. The body could handle the extra flex with the flimsy sheetmetal OEM bumper tying the front of the body together. Now that I have added the very heavy, very rigid Hansen bumper the front ends of the frame rails cannot flex independently of one another. This stress is now localized at the steering box mounting area of the unibody. The vertical portion of the framerail can still flex in and out but the horizontal portion can't so it buckled and cracked.
My conclusion is that you can get away with running a steering box brace as long as you don't have a stiff aftermarket front bumper. I also believe that there is a lot of flexing going on in that part of the unibody and it is much better to allow it to do it's thing than try to stop it and send the stress in a direction that the unibody wasn't designed to handle.
My first question is- How do I fix this? I do not have access to a welder. I will probably end up taking it to a body shop to have it fixed. Can I be content with having them simply weld the crack shut? Or should I have them weld in a strip of sheetmetal along the bottom of the frame rail? I have removed the steering box brace and placed it in a safe location where it will never harm another Cherokee, so I belive the stress that
caused the crack is no longer present. I am also very leery of adding any stiffeners to my frame now that I have seen the consequences of introducing them in places where they do not belong.
The second question is- Do I even need a steering box brace of some kind? I have never found any loose steering box bolts during my routine inspections and there are no signs of cracks or stress around the steering box mounting points. I plan on staying with 33 inch tires and a 4.5 inch lift forever and have no desire to do any hardcore trails.