lfhoward, I added my experience to the pole. My failure mode was a broken planetary gearset. It just let go with no warning. I had a Dodge Intrepid once that used the A606 transmission, which was an earlier front-wheel-drive version of what later became the rear-wheel-drive 42RLE transmission. That car also failed it's planetary gear set without warning at about 150,000 miles. I wonder if Chrysler improved the planetary gears over the years, or if the same gear set just migrated into the new transmission designs. I wonder if there are any oiling improvements that could be made to better protect the planetary gearset. I know racing transmissions are often fitted with external oil pumps and spray jets that squirt oil directly on the gears vs reliance on just splash lubrication.......
Now that I have about 500 miles on my rebuilt transmission, and some more experience with model year variations from roaming around junk yards for parts, I'll add a few more observations.
-regarding removal/replacement of speed sensors. There is no way to remove them on a 2005 with a 42RLE transmission, without removing the front driveshaft. Thought I must be losing my mind, when others said it could be done easily, but then I looked at other Liberty models, and a 2002 and a 2003 I looked at have much more room around the driveshaft and transmission for access to the speed sensors. At least on those models, you could change the speed sensors without removing anything. I know 2003 was also a year that the transmission changed from the 45RFE to the 42RLE, so it's possible that a late 2003 or 2004 has similar good access to the speed sensors with either transmission, but at least beginning in 2005, the clearance just isn't there anymore. It doesn't look like 2006 or 2007 models are any different than 2005, but that would be the last of the KJ body style, before the KK Liberty's came out. Oddly enough, 2005 Libertys had either a flat hood (similar to the Jeep Wrangler) or the usual Liberty hood with the "bumps" to accent the headlights. I don't know if any other differences extended to "under the hood" sheet metal or parts, but my 2005 is a Limited with the "bumps" on the hood.
-The early 45RFE transmission used flared pipe/nut fittings for the transmission cooler lines, while the 42RLE used O-ring/C clip retainer style fittings. While the C clips are simple enough to remove with a small screwdriver or pick, you have to be able to see them to remove them. On my 2005, the oil cooler fittings are only accessible by feel. You can remove the oil cooler bolts and lift or lower it about 1/2" or so (more if you don't mind bending the oil cooler lines), but I quickly discovered they were nearly impossible to remove, without removing the radiator. This allowed me to raise the cooler high enough to see the fittings through the front grille. The 2002-2004 model Liberty's have a different bumper with larger openings below the bumper than 2005-2007 Liberty's. Perhaps it would be easier to access oil cooler fittings on the earlier model bumper, but if a special tool existed to remove or expand the C clip, just by sliding it into position by feel, that would greatly simplify removal. On spring lock fittings (like where the nylon fuel line from the body connects to the metal fuel rail on the engine), there are several tools that make disconnection very easy, just by feel.