The 2006 Jeep Wrangler with the 42RLE 4 speed automatic transmission is known for a problem with the shifter linkage. They used a small plastic bushing to connect the shift arm to the linkage arm on the transmission. This plastic bushing is known to break and/or pop off.
There is a simple fix for this problem. You can replace the plastic bushing and small plastic nipple with a much stronger 3/8 grade 8 bolt. All you need is a wrench and/or ratchet and a drill. Anyone can implement this fix.
You'll need the following...
A drill, a 3/8" 16 1 and 1/2 grade 8 bolt, a 3/8 drill bit, an aircraft (lock) nut, and two 3/8 washers.
Before beginning, place the Jeep in Park, apply the parking brake and chock the wheels.
IMPORTANT: The transmission may potentially change gear during the course of the install, so DO NOT rely on the Park gear to hold the vehicle in place!!
Step 1: The Broken Linkage
This is what the broken linkage looks like. This happened to me on the Rubicon trail, and we bound the linkage with mechanics wire in order to get off the trail.
Step 2: Remove Linkage Arm
Locate the linkage arm on the driver side of the transmission, it should be easy to see. Remove the linkage arm by loosening the bolt on the top of the arm where it comes out of the transmission, and pulling straight up. This bolt clamps the linkage arm to the transmission. There is a square nut which sits in a square groove in the linkage arm. If you remove the bolt completely, this square nut may fall out and you'll need to feel around a bit to retrieve it.
Step 3: Drill Out the Plastic Nipple
Place the linkage arm in a vice, and drill out the plastic nipple with the 3/8 drill bit. The drilled out nipple is pictured sitting on the linkage arm. You should file away the rough edges around the hole.
Step 4: Reinstall the Linkage Arm
Reinstall the linkage arm. While pushing the arm back onto the lever coming vertically out of the transmission, the lever may rotate which changes the gears in the transmission. Rotating the lever all the way counter-clockwise will put the transmission in Park (this is where it should have been when you removed the linkage arm). Secure the linkage arm by tightening the bolt.
The hole at the end of the shifter arm should line up with the hole in the linkage arm.
Insert the 3/8 grade 8 bolt through the hole in the linkage arm, slide a washer over the bolt, slide the bolt with the washer on through the hole in the shifter arm, slide the last washer on the bolt and thread the lock nut in place. Tighten, but do not tighten all the way. You want it to be a little loose so the shift arm can move back and forth freely.
Move the transmission shifter in the cab through all the gears and make sure they engage properly and the shift is smooth. If not, you may need to tighten/loosen the bolt. If the vehicle is not in the gear specified on the transmission shifter, you should check to make sure you had the transmission's lever in the correct location when you reinstalled the linkage arm.
Congratulations, you're done. Your linkage arm should look like that pictured, and you can rest easy knowing that you have a solid grade 8 bolt holding your linkage together rather than a cheap plastic bushing :)
I made it at TechShop :)