I have a 2006 TJ Unlimited with 95k miles on it. At one point under factory warranty one of the lifters failed and it was replaced under the warranty. Now when I drive highway speeds for extended distances It sounds like a POS! I'm not a mechanic but it seems the valvetrain is noisy as well as the manual 6spd transmission, and maybe even sounds like an exhaust leak. I've never changed the tranny oil as the dealer couldn't tell me what to put in, he said "I don't know, just put in gear oil; we do." I do change the oil every 3000 miles with either GTX or Pennsoil and I don't think I've ever ran higher than 3000RPM.
I do have a 100K mile warranty that would cover any transmission problems but that will expire before too long and the dealer is incompetent (see below for example) so I will need to troubleshoot and prove what I find.
This dealer is so incompetent that when we took my wife's Magnum in to replace the passenger seatbelt latch as the internal switch was toast, he replaced two of the four strain gauges. After several more trips back as the airbag computer was inop we got a matched set of four new strain gauges and were back to just a broken switch which I watched him replace under my guidance. And this is the better of the two dealers nearby.
End of rant!!