^^^^Good tips. Check out JeepKJ forum, good source for all things Liberty.
I've had my 05 since 07, got it with 36k on it. As stated, the 42RLE is kind of weak. Got mine rebuilt at 155k. At 163k now. They ride so much better with a proper full spring lift. I was getting ready to trade mine in because of the poor ride, lifted it with OME springs, OME rear shocks, Bilstein front and it rides as nicely as my LR3 and better than my new Cherokee. Handles great too.
Other things to check:
-Make sure it has HOAT coolant in it. If unsure, get it flushed.
-Other than the springs and shocks, the suspension is pretty solid. Just the usual stuff, but at 163k, I'm on my original LCAs up front. UCAs have been replaced with special ones for lifted Liberties. Rear, there was a LCA recall and my UCA back there is the factory one.
-Check for rust by the 3rd brake light
-Do the key trick to check for codes... do off-on (not start)-off-on-off-on and any P codes will come up in the odo.
-Check the CV boot on the tcase end of the front driveshaft. If it hasn't been replaced, it's probably torn. $50 part and easy to swap out. But use it as "garbage on the lawn"
- Likely will leaking oil, comes from front main crank seal and oil pressure sending unit
They're fun vehicles. Love mine. They're safe, great off road and in the snow, and with some suspension upgrades, ride and handle great. Easy to work on and lots of DIY info around.