TJ's do seem to go into 4wheel drive easier when barely moving. The auto trans seem to be even harder. I don't know what tranny you have, but barely get it moving, throw your transmission in neutral, and then pull the lever all the back towards your seat to get it into 4 low. 4 hi is much easier to engage, and can be done on the fly, up to 50mph. But do not try to do that when selecting 4low, you will tear something up. If you have done all this, and still have a problem, try to put it in reverse, to release any pressure on your drive line. It should not take more than 20-30 feet to accomplish that. Now put it in first gear, barely get it rolling, and try to pull it into 4hi, or all the way up into 4low. If this still does not engage your four wheel drive system, then you most likely have a linkage problem with the transfer case, shifter. This is pretty easy to spot if you have someone moving the t-case shifter while you are underneath the Jeep, looking up at the linkage. You should be able to tell if it is hooked up correctly, or not. Sorry to be so lengthy in this explanation. That is why I thought it would just be easier to let the dealer check it out for you, being under warranty and all.