I bought a great condition '05 FX4 Automatic a few months ago. I love everything about it, and have had no issues. Just curious though, what are some common issues with this model that I need to look out for? What are the signs of these issues? I just passed 100k miles on it the other week.

 

The earlier 4.0l SOHC engines had issues with timing chain guides, caused a rattling sound, 2005 should have the newer guides.
Cam synchronizer shaft can get worn and cause high pitched squeal, as this shaft powers the oil pump it needs to be fix at the first sign of trouble.

2005 w/4.0l should have the 5R55E automatic trans, this is an electronically controlled trans, so has solenoids on it that the computer uses to shift gears, these solenoids do fail, but easy to test and replace, each solenoid should show between 20-30ohms, if you have reason to test them.