Rubicon Express RE1670 Trackbar Brace
The uniframe XJ Cherokee has a habit of fatiguing the "framerails" surrounding the engine, causing sloppy steering and handling problems. There's also a good bit of speculation out there that the spreading and movement of the framerails can cause the motor mount bolts to snap, so it makes sense to try to keep those parts tight.
Unlike a normal ladder-frame vehicle like the TJ Wrangler, the XJ uses stamped assemblies to provide needed support to the front end. The RE1670 Trackbar Brace is intended to help prevent some of that loss of handling, but I've got to admit that for it's simplicity it is really one of the more frustrating pieces to install. I actually picked up the Trackbar Brace a year ago and after two half-hearted attempts at installing it I found that it didn't take up much space when stuffed in the back of my storage box.
Rubicon Express intends the RE1670 Brace only for use with their RE1665 Heavy-Duty Trackbar Bracket, as it bolts onto unused holes in the back of the Bracket. The Brace crosses under the oilpan and bolts onto the passenger-side framerail to firm up the front end of the uniframe Cherokee. There are existing holes in the passenger-side rail under the motor mount, so no drilling is involved. Because this passes less than an inch under the oilpan I wouldn't recommend welding it unless you want to pull the engine anytime you need to get into the lower end, say with a Rear Main Seal replacement.
Rubicon Express has also put the installation instructions online, at http://www.rubiconexpress.com/instructions/rubiconexpress/RE1660-1665-1670A.pdf (Adobe Acrobat required)
For mine, getting the right fit meant putting both bolts into the Trackbar Bracket and prying it backward until I got the rearmost hole on the passenger side lined up. After that, I had to remove the upper bolt holding the Brace to the Bracket and rotate the Brace slighly until I could line up the front hole on the passenger side. Once that was in, I could put the upper one in again and begin tightening them up for final installation. None of my 3/4" sockets and wrenches fit the bolts, so I was restricted to using a combo wrench 1/16 of a turn at a time. This is one of those times that reminded me to invest in some ratcheting box wrenches.
The passenger-side of the Trackbar Brace, above the starter (circled)
There's about 3/4" clearance between the oilpan and the Brace, I have heard from some other owners whose rigs had even less space between and were concerned about hitting the oilpan. One Jeeper (I forgot his name) went so far as to make a small spacer that moved the bar down about 1/2" - sort of like a t-case drop.