ax15 poping out of 5th

I have recently bought my 3rd xj and this one has an ax15, I know the transfer case is fubar but that shouldn't make the tranny pop out of 5th on the highway. Are am I looking at a new tranny.

Could be as simple as a worn nylon cap on the end of the shifter. Any grinding? Hard shifting? What lube in the AX15? Specs are GL 3, but that is pretty much history. GL 4 and GL 5 are not right for it. You can buy the new Mopar lube, or use 10w30 motor oil. I chose to use Mobil 1 in mine.

Are your engine and trans mounts any good?

Maybe I should explain on what it is doing.

When I'm cruising on the highway and keep my foot on the gas it stays in gear but as soon as I take my foot off it jumps out of 5th...

I will the take the shifter out and take a look and change the lube in it.

If your engine and trans mounts are toast the trans does a lot of bouncing around between accel and decel--check the mounts.